Muller W.,ARRB Group Ltd. |
Muller W.,University of Queensland |
Scheuermann A.,University of Queensland
Journal of Geophysics and Engineering | Year: 2016
Measuring the electrical permittivity of civil engineering materials is important for a range of ground penetrating radar (GPR) and pavement moisture measurement applications. Compacted unbound granular (UBG) pavement materials present a number of preparation and measurement challenges using conventional characterisation techniques. As an alternative to these methods, a modified free-space (MFS) characterisation approach has previously been investigated. This paper describes recent work to optimise and validate the MFS technique. The research included finite difference time domain (FDTD) modelling to better understand the nature of wave propagation within material samples and the test apparatus. This research led to improvements in the test approach and optimisation of sample sizes. The influence of antenna spacing and sample thickness on the permittivity results was investigated by a series of experiments separating antennas and measuring samples of nylon and water. Permittivity measurements of samples of nylon and water approximately 100 mm and 170 mm thick were also compared, showing consistent results. These measurements also agreed well with surface probe measurements of the nylon sample and literature values for water. The results indicate permittivity estimates of acceptable accuracy can be obtained using the proposed approach, apparatus and sample sizes. © 2016 Sinopec Geophysical Research Institute.
Xu A.,ARRB Group Ltd |
Shayan A.,ARRB Group Ltd |
Shayan A.,Swinburne University of Technology
ACI Materials Journal | Year: 2016
This paper presents results of an investigation on the relationship between reinforcement corrosion rust growth at the concrete-steel interface and cracking of concrete cover, based on study of laboratory specimens containing various amounts of chloride ions. The corrosion depth of steel bars to cause cover cracking (critical depth) was found to vary from 5 μm (0.2 mil) for 24 mm (0.9 in.) bar under 25 mm (1 in.) cover, to 150 μm (5.9 mil) for 6 mm (0.2 in.) bar under 73 mm (2.9 in.) cover. The steel corrosion rate was found to be closely related to the amount of chloride in concrete. The applicability of existing equations on cover cracking is assessed and a new mathematical equation is proposed. The predicted critical corrosion depth by the equation matched with the experimental data reasonably well. A mathematical equation has been proposed for calculation of the time-to-cracking, which uses this model in combination with the law of chloride diffusion in concrete. Copyright © 2016, American Concrete Institute.
Muller W.B.,University of Queensland |
Roberts J.,ARRB Group Ltd.
International Journal of Pavement Engineering | Year: 2013
This study presents a revised approach to conceptualising and analysing data from the traffic speed deflectometer (TSD) which enables full deflection bowl predictions. The approach was successfully applied to TSD surface velocity measurements collected at seven test sites as part of recent Australian trials. More than 1500 deflection bowls produced from the TSD data were validated against approximately 600 40-and 50-kN falling weight deflectometer (FWD) deflection bowl profiles. Overall, the results showed a clear correlation between the shape and magnitude of deflection bowls predicted by both methods. Estimates of maximum deflection (d 0) and structural curvature index (SCI300) from both methods were also compared, showing a strong correlation. The results suggest that the TSD device has significant potential to be used to collect measurements of pavement deflection bowls at highway speeds which are comparable with FWD deflection bowl measurements. © 2013 Copyright Crown copyright © 2013.
Saberi M.,Monash University |
Aghabayk K.,Monash University |
Sobhani A.,ARRB Group Ltd
Physica A: Statistical Mechanics and its Applications | Year: 2015
Individual pedestrian velocities vary over time and space depending on the crowd size, location of individuals' within the crowd, and formation of self-organized lanes. We use empirical data to explore the spatial fluctuations of pedestrian velocities in bidirectional streams. We find that, unlike ordinary fluids, the velocity profile in bidirectional pedestrian streams does not necessarily follow a hyperbolic form. Rather, the shape of the velocity profile is highly dependent on the formation of self-organized lanes. We also show that the spatial fluctuations of pedestrian velocities along and transverse to the flow direction are widely distributed and can be modeled by a sum of Gaussian distributions. Results suggest that the effect of self-organization phenomenon is strong enough that for the same crowd size, the velocity distribution does not significantly change when pedestrians are highly mixed compared to when separate lanes are formed. © 2015 Elsevier B.V. All rights reserved.
Petho L.,ARRB Group Ltd |
Toth C.,Budapest University of Technology and Economics
RILEM Bookseries | Year: 2012
Hot mix asphalt (HMA) performance in terms of fatigue resistance is a well-developed area of pavement design worldwide. Different equipment is available to predict the fatigue performance due to the well supported technical background.Sophisticated pavement design methods utilises the asphalt performance to predict pavement performance and the relative performance comparison between different mix types is also feasible.The research work presented in this paperprovidesan analytical approach to validate laboratory fatigue tests and in-service pavement performance. Large diameter cores (320 mm) were taken from heavily trafficked heavy duty pavement structures and subsequently 2 point bending tests were performed on the cut specimens. The pavement response to loading derived from the FWD measurement was compared to the performance obtained from the laboratory fatigue tests andthe remaining life of the pavement structure was assessed. © RILEM 2012.
Pape T.,ARRB Group Ltd |
Melchers R.,University of Newcastle
Annual Conference of the Australasian Corrosion Association 2014: Corrosion and Prevention 2014 | Year: 2014
The number of publications relating to the good performance of older chloride-contaminated reinforced or prestressed concrete structures continues to rise. This contradicts the majority of corrosion literature concerning structural concrete, which has continuously promoted the negative effects of chlorides since the 1960's. Various standards and guidelines reflect this sentiment, specifying empirical chloride threshold limits that are linked to corrosion risk levels. These have been adopted by industry to inform maintenance and repair procedures. It has also extended to an underlying view that detrimental corrosion may initiate and progress, which may be an incorrect assumption. To address this interpretation, a brief review is provided on the historical development of ideas and research behind chloride-contaminated concrete and associated corrosion-risk, and the subsequent establishment of accepted chloride limits. Results from 2 recent investigations relating to chloride-contaminated concrete are also discussed. A summary discussion on the implications and applications of these findings concludes the paper. This paper identifies that whilst chlorides remain an important consideration in the corrosion process, greater caution is required when assessing structural concrete for corrosion risk based purely on published chloride limits.
Shayan A.,ARRB Group Ltd
Proceedings of Institution of Civil Engineers: Construction Materials | Year: 2016
The effects of alkali-aggregate reaction (AAR) on concrete and structures start at the microstructural level, that is, at molecular and microscopic levels, such as the formation of reaction products in concrete and associated microcracking, which ultimately leads to macro-level effects such as visual cracking, differential movements, displacement and so on. The consequences of these effects are also wide ranging, and depend on the severity of the reaction, the configuration and functions of the affected element and the exposure conditions. The effects of AAR on concrete can range from minor cracking in non-load-bearing elements in benign environments, which may not have any significant consequence, to severe cracking in sensitive structural elements, particularly those exposed to aggressive environments, which could have serious detrimental effects on the mechanical and durability properties of concrete. This paper provides an overview of the changes that occur in the mechanical and durability properties of AAR-affected concrete elements. © 2016, Thomas Telford Services Ltd. All right reserved.
Martin T.,ARRB Group Ltd
Geotechnical Special Publication | Year: 2010
Some 85 of Australia's sealed road network is comprised of unbound granular pavements with a wearing surface treatment of stone aggregate embedded in a thin bituminous binder seal. Experimental pavement deterioration data gathered by means of accelerated load testing (ALT) on various forms of binder seal and stone aggregate over separate test pavements was used to estimate relative performance factors for cumulative rutting and roughness deterioration under these surface treatments. The ALT experiments were under controlled environmental conditions that were either continuously wet or continuously dry to allow modification of these relative performance factors for other environmental conditions. These relative performance factors have been applied to the observed deterioration of given surface treatments to develop road network deterioration (RD) models that allow prediction of the influence of various surface treatments on pavement deterioration. This paper demonstrates that when the relative performance factors are applied to the observed pavement deterioration under a given surface treatment to predict pavement deterioration under other forms of surface treatment, selection of a surface treatment option with the lowest pavement life-cycle cost is possible for a given traffic load and environmental condition. © 2010 ASCE.
Shayan A.,ARRB Group Ltd |
Xu A.,ARRB Group Ltd |
Chirgwin G.,RTA |
Cement and Concrete Research | Year: 2010
Recently, AAR was identified in submerged piles of some bridges in tidal waters. Microstructural examination detected chloroaluminate salts in some cracks. To clarify whether seawater had influenced the deterioration an experimental program was planned to examine the effects of sodium chloride on AAR under various curing conditions. Concrete prisms containing either of highly-reactive, slowly-reactive or nonreactive aggregate, and either low or high alkali contents, were stored in saltwater (representing seawater) or at 100% RH, at temperatures of 38, 60 and 80 °C, for expansion measurement over 600 days, after which the temperature for those stored in saltwater was lowered to 23 °C, to check its effect on further expansion, which could be attributed to precipitation of ettringite and/or Ca-chloroaluminate. The results indicate that the type of aggregate and concrete alkali content had the greatest effect on AAR expansion. Exposure to saltwater did not have any significant effect on the AAR expansion. © 2009 Elsevier Ltd. All rights reserved.
Bennett P.,ARRB Group Ltd
Research Report ARR | Year: 2013
This investigation aimed to describe the distribution of surface characteristics (i.e. macrotexture, rutting and roughness, with the addition of skid resistance (SFC) for the urban network) and the relationship between them, and the relationship of surface characteristics to crash occurrence. The investigation also examined how geometry affected the relationship between surface characteristics and crashes. Additional analysis is carried out to investigate the relationship between macrotexture and crash occurrence in detail, to test the sensitivity of the lengths of section used in the analysis, and to check whether crash occurrence can be related to surface characteristics some distance before the crash site. Data were obtained for a Victorian urban network, a Victorian rural network, and a WA rural network. The crash data covered a five year period; road surface condition data were taken from multi-laser profilometer or SCRIM surveys which were conducted near the middle of the study period; traffic data were the figures estimated by the road authority for the purposes of the Auslink program. Geometry data used in the analysis of the Victorian rural data were obtained from existing Gipsi-trac survey data. The different data elements were linked via the ArcView GIS software, and exported to spreadsheets for analysis. A robust relationship was found between crash rate and macrotexture on Victorian rural roads which agrees well with previous findings from Australia and overseas, although recent New Zealand work found no relationship. Wet weather crashes were not over-represented at low macrotexture sites, but multi-vehicle crashes were. A linear relationship was found for crash rate and roughness; these results agree well with recent work from both New Zealand and Sweden despite differences in crash definitions, road systems and climate. These findings were not replicated on Victorian urban roads, nor on WA rural roads. The reasons for the non- replications are discussed. Possible applications of these findings include providing quantitative information to asset managers about the safety benefits of maintenance interventions, recalibrating maintenance standards to take account of safety benefits, and formulating 'catch up' programs to reduce the extent of poor surface conditions. Studies of the benefits of specific resurfacing projects are required before full confidence can be placed in these results. © ARRB Group Ltd.