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Self-Healing Cementitious Materials
Published in Ghasan Fahim Huseien, Iman Faridmehr, Mohammad Hajmohammadian Baghban, Self-Healing Cementitious Materials, 2022
Ghasan Fahim Huseien, Iman Faridmehr, Mohammad Hajmohammadian Baghban
The ultra-ductile fiber-reinforced cementitious composite also called engineered cementitious composite (ECC) is a special type of concrete that was introduced at the beginning of the 1990s. ECC was continually refined over past two decades [71]. It is highly ductile (3–7%) and displays a tight crack size and a relatively reduced amount of fibers that does not exceed 2% by volume [72]. The distinguishing mechanical quality of the ECC is the metal-like feature. Furthermore, the ECC can withstand heavy loading following crack formation in the context of auxiliary distortions. The self-healing notion of the dry related to the bleeding was investigated by Li et al. [73] regarding the release of chemicals capable of sealing tensile cracks with ulterior air curing. In this manner, the composites without cracks can recover their mechanical properties. However, the self-repair process was displayed low efficiency in case of standard concrete, cement, or fiber-reinforced concrete because the tensile crack size is challenging to control in such materials. A decrease in the tensile load can promote the relentless multiplication of the local breaks within the crack width, leading to the rapid depletion of the repair agents. Hence, it is necessary to reduce the tensile crack width to within tens of micrometers for achieving a successful self-repair. The alternative is to change the mechanical properties of the composites with the use of glass pipes of extremely large size. This was highlighted by several other studies that drew the attention to the significance of the crack width [74].
Synthesis of structural self-repairing and health monitoring
Published in You-Lin Xu, Jia He, Smart Civil Structures, 2017
Engineered cementitious composite (ECC) is a unique type of high performance fibrereinforced cementitious composite, featuring high tensile ductility with moderate fibre volume fraction (2% volume or less) (Yang et al. 2011). Of special interest is that the tensile strain capacity of ECC is 2%–5%, several hundred times that of normal concrete, whereas the compressive strength of ECC ranges from 50 to 80 MPa, putting ECC in the class of high strength concrete materials but without the associated brittleness. With such attractive characteristics, ECC material is expected to have good potential to engage SH in a variety of environmental conditions, and much effort has been made in the investigation of SH with ECC material. For example, the performance of SH of ECC under two different cyclic wetting and drying regimes was investigated by Yang et al. (2009). They found that through SH, crack-damaged ECC recovered 76%–100% of its initial resonant frequency value and attained a distinct rebound in stiffness. Even for specimens deliberately pre-damaged with micro-cracks by loading up to 3% tensile strain, the tensile strain capacity after SH recovered close to 100% that of virgin specimens without any preloading. Moreover, Yang et al. (2011)investigated the healing of early ages (3 days) ECC damaged by tensile preloading after exposure to different conditioning regimes: water/air cycles, water/high temperature air cycles, 90% RH/air cycles and submersion in water. Qian et al. (2010) investigated the SH behaviour of ECC with emphases on the influence of curing condition and pre-cracking time. It was found that for all curing conditions, deflection capacity after SH can recover or even exceed that of virgin samples with almost all pre-cracking ages. Some literature reviews can also be found that introduce the development of SH of ECC (e.g. Li 2003; Wu et al. 2012).
Seismic Strengthening of Unreinforced Concrete Block Masonry Walls with High Ductile Fiber-Reinforced Concrete (HDC)
Published in Journal of Earthquake Engineering, 2023
Wei Zhang, Mingke Deng, Liying Guo, Zhengtao Qiu, Shuo Yang, Zhifang Dong
High ductile fiber-reinforced concrete (HDC), also recognized as engineered cementitious composite (ECC), is a cement-based material reinforced with plastic fibers and features multiple cracking and strain-hardening characteristics in tension (Li, Wang, and Wu 2001; Parra-Montesinos 2005). Kunieda and Rokugo (2006) have indicated that, due to the advantages of the excellent mechanical properties, such composite could limit the development of cracks and enhance the energy consumption and durability of the structural members. Thus, ECC retrofitting strategy has been used to strengthen the reinforced concrete (RC) columns (Deng, Zhang, and Li 2018), reinforced concrete frames with unreinforced masonry infills (Kyriakides and Billington 2014), and beam-column connections (Parra-Montesinos, Peterfreund, and Chao 2005). Dong et al. (2022) have conducted the cyclic diagonal compression tests to investigate the shear response of clay brick masonry panels strengthened with ultra-high ductile concrete (UHDC). The test results proved that UHDC layer retrofitting could significantly enhance the pseudo-ductility and bearing capacity of the URM panels. Lin et al. (2014) have investigated the effect of the ECC shotcrete thickness on the shear capacity and ductility of the clay brick URM panels under the diagonal compression tests; the test results showed a descending return between the thickness of ECC coat and bearing capacity increase obtained. In addition, several experimental studies showed that ECC was an ideal material to improve the brittle failure mode and increase the shear strength and deformation capacity of the unreinforced masonry walls based on the cyclic loading tests (Deng and Yang 2018; Niasar, Alaee, and Zamani 2020). However, researches on ECC-retrofitted concrete block masonry walls still were limited, especially for the in-plane cyclic loading tests.
Fatigue performance of PVA fibre reinforced cementitious composite overlays
Published in International Journal of Pavement Engineering, 2021
Burhan Alam, İsmail Özgür Yaman
Traditional concrete has no mechanism to make it withstand the tensile stresses after a crack occurs, which reduces the stress level of failure under high fatigue cycles (ACI Committee 215 1992). For that, using fibres as reinforcement can improve the tensile strength tremendously in all the concrete region, and at the same time they are easier to use compared to steel rebars (Gopalaratnam and Shah 1987, Balaguru et al. 1992, Zollo 1997, Yao et al. 2003, Song and Hwang 2004). Yet, the improvements depend on a good combination between the fibre type and the matrix of the concrete, which can be only done through a wise selection of fibres, binding materials, aggregate and mix design (Collins et al. 1993, Ferrara et al. 2007, Walraven 2009). A good example of that is a mortar made with a high amount of cement and fly ash (FA) or slag, along with a very fine aggregate, and reinforced with PVA fibres (Li and Kanda 1998). Named Engineered Cementitious Composite (ECC), this type of fibre reinforced concrete has a high strain capacity which allows it to absorb more energy and hence perform much better under dynamic loads (Maalej et al. 2005, Boshoff and van Zijl 2007, Habel and Gauvreau 2008). Besides being ductile, this material has a high durability (Şahmaran and Li 2008), a good wear resistance under traffic loads (Li and Lepech 2004), perform five times better than that of traditional concrete under freezing-thawing conditions (Li et al. 2003), and even prevent corrosion damage when used in reinforced concrete (Kanda et al. 2003, Miyazato and Hiraishi 2005). In addition to all of these, it has a good behaviour under seismic and dynamic loads (Li and Kanda 1998). This is due to the ability of fibres to control and reduce crack nucleation, hence enhance the performance of the structural elements under impact and fatigue loadings (Mindess et al. 2003). However, there is a limited amount of research on the fatigue performance of ECC (Zhang and Li 2002, Leung et al. 2007, Kakuma et al. 2011, Qian et al. 2013).
Experimental and Numerical Model of CFRP Retrofitted Concrete Beams with Intermediate Notches Subjected to Drop-Weight Impact
Published in Structural Engineering International, 2020
N. Bentata, M.L. Bennegadi, Z. Sereir, S. Amziane
To understand the damage behavior of RC beams during impact loading, high speed drop-weight impact tests have been performed. Using the inverse of the beams’ static flexural load capacity, the strain was empirically formulated, with a deflection proportional to the impact energy. Various characteristic values and their relationships were investigated such as the drop height, the static flexural load-carrying capacity, the input impact energy and the beam response values. The results showed that when the resulting impulse was proportional to the impacting mass, the scale factors have been found to differ significantly, depending on whether the drop-weight moved with the beam or rebounded.4 To measure the impact load, acceleration and strain at both the top and bottom surfaces of the concrete beam, the drop-weight impact of concrete beams has been studied experimentally. During impact, the momentum–impulse equilibrium was effectively maintained, indicating that the published records of measured impact force were sufficiently accurate. In addition, the remaining energy was absorbed, particularly through plastic damage to the aluminum alloy.5 An experimental investigation has been conducted to collect fundamental data and to develop more understanding of the effect of steel reinforcement distribution on the dynamic response of reinforced concrete plates. The results obtained showed that the reinforcement ratio had no effect on impulse and absorbed energy values for the same impact load, but crack patterns and failure modes were more dependent on the reinforcement arrangement than on the reinforcement ratio.6 An experimental investigation of concrete slabs under impact load was presented, to compare the performances of concrete samples with and without reinforcement. It was found that slabs with a reinforcing layer offer substantial advantages in resistance to impact load. In addition, slabs with fabric reinforcement were not perforated and the area below these slabs was protected.7 The behavior of reinforced concrete beams manufactured from several concrete types were experimentally and numerically investigated under dynamic impact loading. From this study, the behavior of both normal concrete and engineered cementitious composite (ECC) beams showed that the smallest cracks formed on the test specimens manufactured using ECC and the largest cracks formed on the test specimens manufactured using low-strength concrete. In addition, the type of material significantly affected the width of cracks observed on the specimens tested.8