Effect of Heterogeneity in Micro-Structure and Micro-Strength on the Discrepancies Between Direct and Indirect Tensile Tests on Brittle Rock

ABSTRACTIn inspections of buildings, it is common to find structures that, well before reaching its useful life longer require repairs and reinforcements. This study examined the bond strength between concrete of different ages and between steel and concrete, focusing on the recovery of reinforced concrete structures. To analyze the bond between concrete of different ages, trials with specimens receiving three different types of treatments at the interface between the concrete were performed: brushing; brushing and mortar equal to concrete of substrate and brushing and epoxy layer. Indirect tensile tests and oblique and vertical shear tests at the interface were made . The bond stress between steel and concrete was evaluated by pull out test under the conditions of the bar inserted in the still fresh concrete and when inserted in the hardened concrete with epoxy. Results showed increased bond strength by indirect tensile stress of 15% and 37%; 4% and 12% for the adherence test by oblique shear, and 108% and 178%, for the testing of vertical shear, respectively, for the specimens whose interfaces have received, in addition to brushing, layer of mortar and epoxy bridge, compared to those who received only brushing. Insignificant loss (about 0.52%) of bond stress was noticed for pull out test of steel bar when compared with test results of the specimens that had steel bar inserted in the concrete in the hardened state with epoxy adhesion bridge, with those who had inserted steel bar in fresh concrete.

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Tensile Testing of Soils: History, Equipment and Methodologies

Civil Engineering Journal ◽

10.28991/cej-2020-03091494 ◽

2020 ◽

Vol 6 (3) ◽

pp. 591-601

Author(s):

Ausamah Al Houri ◽

Ahed Habib ◽

Ahmed Elzokra ◽

Maan Habib

Keyword(s):

Tensile Strength ◽

State Of The Art ◽

Retaining Walls ◽

Tensile Tests ◽

Testing Methods ◽

Embankment Dams ◽

Current State ◽

Wide Range ◽

Indirect Tensile ◽

And Behavior

Tensile strength of soil is indeed one of the important parameters to many civil engineering applications. It is related to wide range of cracks specially in places such as slops, embankment dams, retaining walls or landfills. Despite of the fact that tensile strength is usually presumed to be zero or negligible, its effect on the erosion and cracks development in soil is significant. Thus, to study the tensile strength and behavior of soil several techniques and devices were introduced. These testing methods are classified into direct and indirect ways depending on the loading conditions. The direct techniques including c-shaped mold and 8-shaped mold are in general complicated tests and require high accuracy as they are based on applying a uniaxial tension load directly to the specimen. On the other hand, the indirect tensile tests such as the Brazilian, flexure beam, double punch and hollow cylinder tests provide easy ways to assess the tensile strength of soil under controlled conditions. Although there are many studies in this topic the current state of the art lack of a detailed article that reviews these methodologies. Therefore, this paper is intended to summarize and compare available tests for investigating the tensile behavior of soils.

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Differences in the Ageing Behavior of Asphalt Pavements with Porous and Stone Mastic Asphalt Mixtures

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/03611981211032218 ◽

2021 ◽

pp. 036119812110322

Author(s):

Ruxin Jing ◽

Aikaterini Varveri ◽

Xueyan Liu ◽

Athanasios Scarpas ◽

Sandra Erkens

Keyword(s):

Asphalt Pavement ◽

Tensile Tests ◽

Asphalt Pavements ◽

Porous Asphalt ◽

Mastic Asphalt ◽

Stone Mastic Asphalt ◽

Aggregate Packing ◽

Indirect Tensile ◽

The Fourier Transform ◽

Air Void

The degradation of bituminous materials as a result of ageing has a significant effect on asphalt pavement performance. In this study, one porous asphalt (PA) section and one stone mastic asphalt (SMA) asphalt pavement section were designed and constructed in 2014 and exposed to the actual environmental condition. To study the change in the pavement’s mechanical properties, asphalt cores were collected from both test sections annually. The change in stiffness modulus was determined via cyclic indirect tensile tests. To investigate the ageing behavior across the pavement depth, the bitumen was extracted and recovered from 13 mm slices along the depths of the cores. The chemical composition and rheological properties of the field-recovered bitumen, and that of original bitumen aged in standard short- and long-term ageing protocols, were investigated by means of the Fourier Transform Infrared (FTIR) spectrometer and Dynamic Shear Rheometer. The results show that the effect of mineral aggregate packing, and therefore of air-void distribution and connectivity, on the ageing sensitivity of the pavements with time was significant, as the changes in the stiffness of the PA mixture were greater than that of SMA mixture. In addition, the results of field-recovered bitumen show that there is an ageing gradient inside the porous asphalt layer, however, the ageing of SMA mainly happens on the surface of the layer. Finally, the field-recovered and laboratory-aged bitumen results demonstrate a weak relation between field and standard laboratory ageing protocols.

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Experimental Investigation on Nonlinear Flow Anisotropy Behavior in Fracture Media

Geofluids ◽

10.1155/2019/5874849 ◽

2019 ◽

Vol 2019 ◽

pp. 1-9 ◽

Cited By ~ 4

Author(s):

Chun Zhu ◽

Xiaoding Xu ◽

Xiuting Wang ◽

Feng Xiong ◽

Zhigang Tao ◽

...

Keyword(s):

Tensile Tests ◽

Nonlinear Flow ◽

Scanning System ◽

Affine Surface ◽

Proposed Model ◽

Indirect Tensile ◽

New Formula ◽

Flow Anisotropy ◽

Flow Experiments ◽

Forchheimer’S Law

A series of flow experiments were performed on matched fractures to study the problem of non-Darcy flow in fractured media. Five rock fractures of different roughness were generated using indirect tensile tests, and their surface topographies were measured using a stereo topometric scanning system. The fracture was assumed to be a self-affine surface, and its roughness and anisotropy were quantified by the fractal dimension. According to the flow tortuosity effect, the nonlinear flow was characterized by hydraulic tortuosity and surface tortuosity power law relationships based on Forchheimer’s law. Fracture seepage experiments conducted with two injection directions (0° and 90°) showed that Forchheimer’s law described the nonlinear flow well. Both the proposed model and Chen’s double-parameter model gave similar results to the experiment, but the match was closer with the proposed model. On this basis, a new formula for the critical Reynolds number is proposed, which serves to distinguish linear flow and Forchheimer flow.

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From Complex Modulus E* to Creep Compliance D(t): Experimental and Modeling Study

Materials ◽

10.3390/ma13081945 ◽

2020 ◽

Vol 13 (8) ◽

pp. 1945

Author(s):

Abdeldjalil Daoudi ◽

Daniel Perraton ◽

Anne Dony ◽

Alan Carter

Keyword(s):

Tensile Test ◽

Creep Compliance ◽

Complex Modulus ◽

Tensile Tests ◽

Direct Compression ◽

Creep Tests ◽

Indirect Tensile Test ◽

2S2p1d Model ◽

Indirect Tensile ◽

Direct Tensile

Creep compliance (D(t)) is a very important input for the thermal cracking resistance in the Mechanistic-Empirical Pavement Design Guide (MEPDG). The aim of the work presented here is to predict the results of creep compliance D(t) from the result of complex modulus E*(ω). The work plan is divided in two main parts: an experimental part consisting of creep tests, and a modeling part. Three configurations were compared together, namely direct tensile, direct compression and indirect tensile tests. The modelling part consists of using a 2S2P1D model coupled to Kopelman approximation to switch from the frequency domain to the time domain. Additionally, 2S2P1D was used to calibrate the generalized Kelvin–Voigt model and get the creep compliance directly from E* results. The experimental results show that D(t) from direct tensile and direct compression are the same in the viscoelastic domain and are greater than D(t) from the indirect tensile test. The indirect tensile test (IDT) seems to be very difficult to achieve compared to the other two variants. The converted results using the 2S2P1D model coupled to Kopelman approximation and the results from the GKV model describe the experimental points very well.

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