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1、建筑工程毕业设计外文翻译英文原文The effects of surface preparation on the fracture behavior of ECC/concrete repair systemToshiro Kamada a,*, Victor C Li ba Department of Civil Engineering, Gifu University, Yanagido, Gifu 501-1193, Japanb Advanced Civil Engineering Materials Research Laboratory, Department of Civil
2、and Environmental Engineering,University of Michigan, Ann Arbor, Michigan, MI 48109-2125, USAReceived 7 July 1999; accepted 15 May 2000AbstractThis paper presents the influence of surface preparation on the kink-crack trapping mechanism of engineered cementitious composite (ECC)/concrete repair syst
3、em In general, surfacepreparation of the substrate concrete is considered essential to achieve a durable repair In thisexperiment, the smooth surface* system showed more desirable behavior in the crack pattern and the crack widths than the rough surface* system This demonstrates that the smooth surf
4、ace system is preferable to the rough surface system, from the view point of obtaining durable repair structure The special phenomenon of kink-crack trapping which prevents the typical failuremodes of delamination or spalling in repaired systems is best revealed when the substrate concrete is prepar
5、ed to have a smooth surface prior to repair This is in contrast to the standard approach when the substrate concrete is deliberately roughened to create better bonding to the new concrete 0 2000 Elsevier Science Ltd All rights reservedKeywords: ECC repair system; Kink-crack trapping mechanism; Surfa
6、ce preparation; Durable repair1 IntroductionEngineered cementitious composites (ECCs) 1,2J are high performance fiber-reinforced cement based composite materials designed with micromechanical principles Micromechanicalparameters associated with fiber, matrix and interface are combined to satisfy a p
7、air of criteria, the first crack stress criterion and steady state cracking criterion 3 to achieve the strain hardening behavior Micromechanics allows optimization of the composite for high performance while minimizing the amount of reinforcing fibers (generally less than 2-3%) ECC has a tensile str
8、ain capacity of up to 6% and exhibits pseudo-strain hardening behavior accompanied by multiple cracking It also has high ultimate tensile strength (5-10 MPa), modulus of rupture (8-25 MPa), fracture toughness (25-30 kj/m2) and compressive strength (up to 80 MPa) and strain (0.6%). A typical tensile
9、stressstrain curve is shown in Fig 1 ECC has its uniqueness not only insuperior mechanical properties in tension or in relatively small amount ofchopped fiber usage but also in micromechanical methodology in material design.The use of ECC for concrete repair was proposed by Li et al4, and Lim and Li
10、 5 In theseexperiments, specimens representative of an actual repair system 一 bonded overlay of a concrete pavement above a joint, were used It was shown that the common failure phenomenona ofspalling or delamination in repaired concrete systems were eliminated Instead, microcracksemanated from the
11、tips of defects on the ECC/concrete interface, kinked into and subsequently were arrested in the ECC material (see Fig 2, 5) The tendency for the interface crack to kink into the ECC material depends on the competing driving force for crack extension at differentorientations, and on the competing cr
12、ack extension resistance along the interface and into the ECC materia1. A low initial toughness of ECC combined with a high Mode II loading configuration tends to favor kinking However, if the toughness of ECC remains low after crack kinking, this crack will propagate unstably to the surface, formin
13、g a surface spal1 This is the typically observed phenomenon associated with brittle concrete and even fiber-reinforced concrete (FRC) In the case of ECC, the kinked crack is trapped or arrested in the ECC material, due to the rapidly rising toughness of the ECC materia1. Conceptually, the ECC behave
14、s like a material with strong R-curve behavior, with low initial toughness similar to that of cement (0.01 kj/m2) and high plateau toughness (25-30 kj/m2) After kinked crack arrest, additional load can drive further crackextension into the interface, followed by subsequent kinking and arrestDetails
15、of the energetics of kink-crack trapping mechanism can be found in 5 It was pointed out that this kink-crack trapping mechanism could serve as a means for enhancing repaired concrete system durability.In standard concrete repair, surface preparation of the substrate concrete is considered critical i
16、n achieving a durable repair 6_ In the study of Lim and Li 5, the ECC is cast onto a diamond saw cut surface of the concrete Hence, the concrete surface is smooth and is expected as a result to produce a low toughness interface Higher interface roughness has been associated with higher interface toughness in bi-material systems 7In this paper, this particular aspect of the influence of surfac
