Precision of Shear Tests in Evaluating Asphalt Mixtures

2003 ◽  
Vol 1832 (1) ◽  
pp. 155-160 ◽  
Author(s):  
R. Michael Anderson ◽  
Richard K. Steger ◽  
Gerald A. Huber ◽  
Pedro Romero
Keyword(s):  
Mechanical Properties ◽  
Hot Mix Asphalt ◽  
Shear Stiffness ◽  
Asphalt Mixtures ◽  
Shear Tests ◽  
Frequency Sweep ◽  
Constant Height ◽  
Repeated Load ◽  
Shear Tester ◽  
Highway Research

Various methods exist to measure the mechanical properties of hot-mix asphalt (HMA). To be useful such a test not only must measure a property that controls performance but also must be repeatable. The Strategic Highway Research Program developed tests with the Superpave® shear tester that have been shown to be related to HMA performance. To date, repeatability has not been quantified. The results of a repeatability study for the measurement of shear stiffness (frequency sweep) and of permanent shear strain (repeated-load, constant-height testing) are reported.

scholarly journals The Effect of Ageing on Chemical and Mechanical Properties of Asphalt Mortar

2018 ◽  
Vol 8 (11) ◽  
pp. 2231 ◽  
Author(s):  
Ruxin Jing ◽  
Xueyan Liu ◽  
Aikaterini Varveri ◽  
Athanasios Scarpas ◽  
Sandra Erkens
Keyword(s):  
Mechanical Properties ◽  
Asphalt Mixtures ◽  
Pavement Performance ◽  
Frequency Sweep ◽  
Carbonyl Index ◽  
Mineral Particles ◽  
Tension Tests ◽  
Ftir Spectrometry ◽  
Diffusion Paths ◽  
Asphalt Mortar

Asphalt mortar is a mixture of bitumen, filler, and sand. Mortar plays an important role in asphalt mixtures as it serves as the adhesive between the coarser aggregates. Due to the effect of bitumen ageing, the chemical and mechanical properties of asphalt mortar evolve with time. The mortar becomes more brittle and prone to cracking, thus leading to inferior pavement performance. In this study, Fourier transform infrared (FTIR) spectrometry was used to quantify changes in the chemical functional groups related to ageing and to calculate the carbonyl and sulfoxide indices. In addition, frequency sweep tests and uniaxial tension tests were performed by means of dynamic shear rheometer (DSR) tests to determine evolution of the stiffness and strength due to ageing. Two different oven ageing protocols were used to evaluate the effect of fine mineral particles on bitumen ageing. The protocols differed with respect to the order of ageing and mixing of the constituents. The results showed that both the chemical and mechanical properties of mortars significantly changed with ageing. Specifically, the carbonyl index, stiffness, and strength of the mortar increased. Under the same ageing conditions, a higher ageing level was observed for mortars produced by first mixing and then ageing compared to the mortars produced by mixing aged bitumen with filler and sand. This could be due to the presence of sand and filler particles, which resulted in an increased length of diffusion paths and consequently a slower ageing process.

scholarly journals Influence of compaction temperature on the properties of Marshall specimens

2015 ◽  
Vol 10 (4) ◽  
pp. 309-315 ◽  
Author(s):  
Ivica Androjić ◽  
Sanja Dimter
Keyword(s):  
Mechanical Properties ◽  
Structural Design ◽  
Hot Mix Asphalt ◽  
Asphalt Mixture ◽  
Maximum Density ◽  
Asphalt Mixtures ◽  
Test Results ◽  
Compaction Temperature ◽  
Asphalt Mix ◽  
Very High

Compaction of hot mix asphalt is influenced by several factors; some related to the environment, some determined by mix and structural design and some by contractor during construction. The temperature of asphalt mixture has the biggest influence on the compaction of asphalt mixtures and their properties. The temperature of asphalt mixture affects viscosity of bitumen and achievement of the maximum density of asphalt mixture. This paper describes a laboratory study on the effects of different installation temperatures on the physico-mechanical properties of specimens of asphalt mixtures: stability, Marshall Quotient (stiffness), density, voids and voids filled with asphalt. By regression analysis of the test results the correlation of certain properties of asphalt mix and compaction temperatures was established. For all the models observed, the coefficients of determination are very high and indicate very solid links. The obtained research results indicate a pronounced effect of compaction temperature on each tested property of asphalt mix.

Tire Treadwear — A Comprehensive Evaluation of the Factors: Generic Type, Aspect Ratio, Tread Pattern, and Tread Composition Part IV: Laboratory Measurement of Mechanical Properties and Mechanical Actions of Tires Relating to Treadwear

1986 ◽  
Vol 14 (4) ◽  
pp. 264-291
Author(s):  
K. L. Oblizajek ◽  
A. G. Veith
Keyword(s):  
Mechanical Properties ◽  
Shear Stress ◽  
Contact Zone ◽  
Flexural Rigidity ◽  
Comprehensive Evaluation ◽  
Shear Stiffness ◽  
Shear Stresses ◽  
Lateral Shear ◽  
Band Bending ◽  
Tread Rubber

Abstract Treadwear is explained by specific mechanical properties and actions of tires. Rubber shear stresses in the contact zone between the tire and the road become large at large slip angles. When normal stresses are insufficient to prevent sliding at the rear of the footprint, wear occurs at a rate that depends on test severity. Two experimental approaches are described to relate treadwear to tire characteristics. The first uses transducers imbedded in a simulated road surface to obtain direct measurements of contact stresses on the loaded, freely-rolling, steered tires. The second approach is developed with the aid of a simple carcass, tread-band, tread-rubber tire model. Various tire structural configurations; characterized by carcass spring rate, edgewise flexural band stiffness, and tread rubber shear stiffness; are simulated and lateral shear stress response in the contact zone is determined. Tires featuring high band stiffness and low carcass stiffness generate lower lateral shear stress levels. Furthermore, coupling of tread-rubber stiffness and band flexural rigidity are important in determining level of shear stresses. Laboratory measurements with the described apparatus produced values of tread-band bending and carcass lateral stiffness for several tire constructions. Good correlation is shown between treadwear and a broad range of tire stiffness and test course severities.

scholarly journals Nonlinear modelling of the seismic response of masonry structures: Calibration strategies

2021 ◽  
Author(s):  
Antonio Maria D’Altri ◽  
Francesco Cannizzaro ◽  
Massimo Petracca ◽  
Diego Alejandro Talledo
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
Shear Stiffness ◽  
Model Material ◽  
National Standards ◽  
National Standard ◽  
Masonry Structures ◽  
Nonlinear Modelling ◽  
Various Boundary Conditions ◽  
Panel Stiffness

AbstractIn this paper, a simple and practitioners-friendly calibration strategy to consistently link target panel-scale mechanical properties (that can be found in national standards) to model material-scale mechanical properties is presented. Simple masonry panel geometries, with various boundary conditions, are utilized to test numerical models and calibrate their mechanical properties. The calibration is successfully conducted through five different numerical models (most of them available in commercial software packages) suitable for nonlinear modelling of masonry structures, using nonlinear static analyses. Firstly, the panel stiffness calibration is performed, focusing the attention to the shear stiffness. Secondly, the panel strength calibration is conducted for several axial load ratios by attempts using as reference the target panel strength deduced by well-known analytical strength criteria. The results in terms of panel strength for the five different models show that this calibration strategy appears effective in obtaining model properties coherent with Italian National Standard and Eurocode. Open issues remain for the calibration of the post-peak response of masonry panels, which still appears highly conventional in the standards.

scholarly journals The Infuence of Salicin on Rheological and Film-Forming Properties of Collagen

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1661
Author(s):  
Katarzyna Adamiak ◽  
Katarzyna Lewandowska ◽  
Alina Sionkowska
Keyword(s):  
Mechanical Properties ◽  
Atomic Force Microscopy ◽  
Infrared Spectroscopy ◽  
Rheological Properties ◽  
Silver Carp ◽  
Shear Tests ◽  
Force Microscopy ◽  
Atomic Force ◽  
Film Forming ◽  
Potential Applications

Collagen films are widely used as adhesives in medicine and cosmetology. However, its properties require modification. In this work, the influence of salicin on the properties of collagen solution and films was studied. Collagen was extracted from silver carp skin. The rheological properties of collagen solutions with and without salicin were characterized by steady shear tests. Thin collagen films were prepared by solvent evaporation. The structure of films was researched using infrared spectroscopy. The surface properties of films were investigated using Atomic Force Microscopy (AFM). Mechanical properties were measured as well. It was found that the addition of salicin modified the roughness of collagen films and their mechanical and rheological properties. The above-mentioned parameters are very important in potential applications of collagen films containing salicin.

scholarly journals Applicability of a Three-Layer Model for the Dynamic Analysis of Ballasted Railway Tracks

Vibration ◽  
2021 ◽  
Vol 4 (1) ◽  
pp. 151-174
Author(s):  
André F. S. Rodrigues ◽  
Zuzana Dimitrovová
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Dynamic Analysis ◽  
Shear Stiffness ◽  
Shear Resistance ◽  
Railway Track ◽  
Fe Model ◽  
Inertial Effects ◽  
Layer Model ◽  
3D Finite Element

In this paper, the three-layer model of ballasted railway track with discrete supports is analyzed to access its applicability. The model is referred as the discrete support model and abbreviated by DSM. For calibration, a 3D finite element (FE) model is created and validated by experiments. Formulas available in the literature are analyzed and new formulas for identifying parameters of the DSM are derived and validated over the range of typical track properties. These formulas are determined by fitting the results of the DSM to the 3D FE model using metaheuristic optimization. In addition, the range of applicability of the DSM is established. The new formulas are presented as a simple computational engineering tool, allowing one to calculate all the data needed for the DSM by adopting the geometrical and basic mechanical properties of the track. It is demonstrated that the currently available formulas have to be adapted to include inertial effects of the dynamically activated part of the foundation and that the contribution of the shear stiffness, being determined by ballast and foundation properties, is essential. Based on this conclusion, all similar models that neglect the shear resistance of the model and inertial properties of the foundation are unable to reproduce the deflection shape of the rail in a general way.

scholarly journals Evaluations of Nano-Sized Hydrated Lime on the Moisture Susceptibility of Hot Mix Asphalt Mixtures

2012 ◽  
Vol 174-177 ◽  
pp. 82-90 ◽  
Author(s):  
Ju Nan Shen ◽  
Zhao Xing Xie ◽  
Fei Peng Xiao ◽  
Wen Zhong Fan
Keyword(s):  
Tensile Strength ◽  
Experimental Design ◽  
Hot Mix Asphalt ◽  
Hydrated Lime ◽  
Asphalt Mixtures ◽  
Indirect Tensile Strength ◽  
Moisture Resistance ◽  
Strength Ratio ◽  
Moisture Susceptibility ◽  
Indirect Tensile

The objective of this study was to evaluate the effect of nano-sized hydrated lime on the moisture susceptibility of the hot mix asphalt (HMA) mixtures in terms of three methodologies to introduce into the mixtures. The experimental design for this study included the utilizations of one binder source (PG 64-22), three aggregate sources and three different methods introducing the lime. A total of 12 types of HMA mixtures and 72 specimens were fabricated and tested in this study. The performed properties include indirect tensile strength (ITS), tensile strength ratio (TSR), flow, and toughness. The results indicated that the nano-sized lime exhibits better moisture resistance. Introducing process of the nano-sized lime will produce difference in moisture susceptibility.

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