Fracture characterization of concrete/epoxy interface affected by moisture

Lau, Denvid; Büyüköztürk, Oral

doi:10.1016/j.mechmat.2010.09.001

Cited by 139 publications

(56 citation statements)

References 31 publications

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“…In wet conditions, water molecules can seep into the gaps generated by the hair-like structures and eventually weaken the adhesion at the interface as reported in a recent study of the interfacial integrity between a single polymer chain and a silica substrate, using molecular modeling (19,20). An earlier study of concreteepoxy interfaces indicated that Γ i usually ranged between 10 J/m 2 and 20 J/m 2 for the dry case and between 5 J/m 2 and 10 J/m 2 for the wet case (21). Such consistency implies that using silica as a substitute for concrete is a reasonable approach in the modeling and simulation process.…”

Section: Resultsmentioning

confidence: 75%

A robust nanoscale experimental quantification of fracture energy in a bilayer material system

Lau

Broderick

Buehler³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Accurate measurement of interfacial properties is critical any time two materials are bonded-in composites, tooth crowns, or when biomaterials are attached to the human body. Yet, in spite of this importance, reliable methods to measure interfacial properties between dissimilar materials remain elusive. Here we present an experimental approach to quantify the interfacial fracture energy Γ i that also provides unique mechanistic insight into the interfacial debonding mechanism at the nanoscale. This approach involves deposition of an additional chromium layer (superlayer) onto a bonded system, where interface debonding is initiated by the residual tensile stress in the superlayer, and where the interface can be separated in a controlled manner and captured in situ. Contrary to earlier methods, our approach allows the entire bonded system to remain in an elastic range during the debonding process, such that Γ i can be measured accurately. We validate the method by showing that moisture has a degrading effect on the bonding between epoxy and silica, a technologically important interface. Combining in situ through scanning electron microscope images with molecular simulation, we find that the interfacial debonding mechanism is hierarchical in nature, which is initiated by the detachment of polymer chains, and that the three-dimensional covalent network of the epoxy-based polymer may directly influence water accumulation, leading to the reduction of Γ i under presence of moisture. The results may enable us to design more durable concrete composites that could be used to innovate transportation systems, create more durable buildings and bridges, and build resilient infrastructure. molecular mechanics | bimaterial systems | superlayer | energy release | biomedical I nterfaces exist whenever materials are bonded together and can be found frequently in both natural and synthetic bonded systems, for instance, the mineral-protein interfaces in animals, interfaces between different phases in composite materials, the enamel-polymer interfaces involved in dental treatment, or the cell-substrate interfaces in biomedical applications (1−7). The integrity of the interface under various environmental conditionsincluding different temperature and moisture levels-is critical to many applications (8−10). Meanwhile, because of the advancement and development in technology, a large number of bonded systems in various engineering applications are needed, possessing increasingly higher accuracy in design and manufacturing process in a very small length scale. However, currently, a robust and generally applicable methodology to quantify the fracture energy at these interfaces from a microscopic perspective is lacking.Several straightforward measurement methods for quantifying the interfacial fracture energy on large specimens, such as direct peel/shear specimen (11, 12), Brazilian disk specimen (13), and sandwiched beam specimen (14, 15), have been reported. However, it has been difficult to directly measure this parameter for microscale...

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Section: Resultsmentioning

confidence: 75%

A robust nanoscale experimental quantification of fracture energy in a bilayer material system

Lau

Broderick

Buehler³

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Fracture energy of the interface is considered as a main parameter representing the interface fracture behaviour by many researchers (Kunieda et al 2000;Martinola et al 2001;Lau and Büyüköztürk 2010). Cement based materials exhibit a non-linear stress-strain relationship and microcracking before the peak stress.…”

Section: Simulation Results and Discussionmentioning

confidence: 99%

Micromechanical Study of the Interface Properties in Concrete Repair Systems

Luković

Šavija

Dong

et al. 2014

ACT

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Micromechanical interface properties in a concrete repair system determine the performance and reliability of a repaired structure. In order to characterize these properties, nanoindentation technique was applied. Three different repair material mixtures, based on Portland cement or partial replacement of Portland cement with blast furnace slag, were tested. Hardness and elastic modulus values obtained from the nanoindentation were used directly as input for simulated direct tension test. This way, the fracture behaviour of original microstructure, "mimicked" by Delft lattice model, is analysed. Backscattered electron (BSE) image analysis is utilized to estimate the average size of the interface zone which is distinguished as locally more porous area. This, together with simulation results, is further used for calculation of the interface stiffness. Simulation results enable prediction and better insight into fracture propagation and micromechanical response of the tested zone. They also indicate the ratio between interface and bulk material fracture properties when different types of repair materials are used. Load displacement diagrams of interface, old and new material can serve as an input for numerical modelling and understanding of fracture behaviour of the repair systems at the higher scale. Potentially, this approach may develop as a tool for verifying and engineering interface properties such that desired performance of the repaired structure is achieved.

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“…Since some detrimental effects of moisture on the mechanical properties of FRP/concrete assemblies have been reported, especially with the use of cold-curing epoxy adhesives [11,13,14], and since the rate of moisture diffusion increases with temperature, hygrothermal ageing conditions are considered in the present study. Moreover, as underlined by Yun and Wu [15], the durability of FRP/concrete joints under freezethaw cycling has received insufficient attention, and contradictory results were reported by different authors.…”

Section: Introductionmentioning

confidence: 99%