Comparative evaluation of an experimental binder in hot-mix asphalt : correlating the predicted performance of the binder with asphalt testing

Paper presented at the 33rd Annual Southern African Transport Conference 7-10 July 2014 "Leading Transport into the Future", CSIR International Convention Centre, Pretoria, South Africa.The binder is an important constituent of an asphalt mix and it affects the overall performance of the mix, especially with regards to permanent deformation and fatigue cracking. The stiffest binder available from the Chevron refinery in the Western Cape is a 70/100 penetration grade bitumen. This has resulted in numerous role players in the industry developing experimental binders (closer in stiffness to a 50/70 penetration grade binder) to provide an improved performance with regards to asphalt applications. This paper presents the evaluation of an experimental binder in terms of comparisons with 50/70 penetration grade bitumen of known good performance. Comparative testing was done using the current South African bitumen specification as well as performance grade properties with reference to AASHTO MP19 / M320 and the complex shear moduli. Furthermore, the comparative performance of the binders in identical asphalt mixes containing the same aggregate, grading and binder content were evaluated. The asphalt performance-related tests conducted on the mixes included repeated axial load permanent deformation (rutting indicator), beam fatigue (cracking indicator), dynamic modulus (stiffness indicator) and modified Lottman (durability indicator). The test results were evaluated comparatively to establish whether the performance of the asphalt mixes differed. The close correlations between some binder tests and the asphalt tests in predicting performance were found to be of interest.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by CE Projects cc. Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected]

The effect of trafficking on the rheological properties of binder recovered from a one year old road

Asphalt cores were sampled from four sites along a major route in Tanzania, where asphalt surfacing was constructed approximately one year ago. The bituminous binder was recovered from cores taken from the wheel path as well as from cores taken from the shoulder, in order to assess whether the action of vehicular trafficking had any effect on the rheological properties of the recovered binders. A range of rheological tests were conducted on the recovered binder, including empirical tests such as penetration and softening point, as well as more fundamental tests such as the G*/sin? and the multi-stress creep recovery test.Paper presented at the 35th Annual Southern African Transport Conference 4-7 July 2016 "Transport ? a catalyst for socio-economic growth and development opportunities to improve quality of life", CSIR International Convention Centre, Pretoria, South Africa.The Minister of Transport, South AfricaTransportation Research Board of the US

Evaluation of the performance of aggregate in hot-mix asphalt

Paper presented at the 33rd Annual Southern African Transport Conference 7-10 July 2014 "Leading Transport into the Future", CSIR International Convention Centre, Pretoria, South Africa.The overall performance of an asphalt mix is dependent on, amongst others, the properties of the constituent materials, which include aggregate, binder and filler. The aggregate for production of asphalt mixes is usually sourced from a quarry, which is established through a long and expensive process. A quick evaluation of a new aggregate source will give some indication of its future performance as well as facilitate its introduction into the market place. This paper presents a study of the comparative performance of two aggregates; a granite aggregate of known good performance and a relatively unknown quartzite aggregate containing up to 30% shale. The basic properties of the quartzite aggregate were assessed; following which, the performance of the aggregate in an asphalt mix was evaluated. The design grading of the asphalt mixes was similar; the only difference being that the coarse granite fractions (6.7 and 9.5 mm) of the asphalt mix of known good field performance were replaced by coarse quartzite fractions. The same binder type and crusher sand was used in both asphalt mixes, allowing for a comparative evaluation of the mixes in the laboratory. The asphalt performance-related tests conducted on the mixes included Repeated Simple Shear Test at Constant Height (rutting indicator), beam fatigue test (cracking indicator), dynamic modulus (stiffness indicator) and modified Lottman test (durability indicator). The test results were analysed statistically, to establish whether the performance of the asphalt mixes differed.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by CE Projects cc. Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected]

Quantification of aggregate grain shape characteristics using 3-D laser scanning technology

Paper presented at the 32nd Annual Southern African Transport Conference 8-11 July 2013 "Transport and Sustainable Infrastructure", CSIR International Convention Centre, Pretoria, South Africa.Aggregate shape and surface characteristics influence the performance of both bound and unbound pavement materials. This paper presents some results of an on-going study on the characterization of aggregates using a three-dimensional (3-D) laser scanner technology. A sample of coarse aggregate andesite particles passing 19.0 mm and retained on 13.2 mm sieve was used for the study. The 3-D images from the laser scanning device were fully utilized in quantifying the shape descriptors in order to identify the differences between individual aggregates. It was possible to quantify differences in particle shape characteristics at the small particle scale. The study has demonstrated the advantages of the innovative 3-D laser scanning technology to quantify the shape characteristics of aggregate particles.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: nigel@doctech URL: http://www.doctech.co.zamv201

Crushing damage estimation for pavement with lightly cementitious bases

This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by CE Projects cc. Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: [email protected] presented at the 33rd Annual Southern African Transport Conference 7-10 July 2014 "Leading Transport into the Future", CSIR International Convention Centre, Pretoria, South Africa.Crushing (or compression) failure and associated surface deformation of lightly cementitious (stabilised) materials used for base/sub-base course layers in pavements has been well established in the South African pavement design practice since the 1990s. Typically, crushing failure starts at the surface of the cementitious base layer, and could extend to 50 mm deep, depending on tyre load/stress conditions. Recently developed crushing damage relationships for 2, 5, 10, 15 and 20 mm level of deformation (“rut”) were proposed for practical application on these pavements. The aim of this paper is the practical application of these relationships for an un-surfaced and surfaced pavement with a typical stabilised (C3 – quality) base layer. Currently there are up to 15 standard pavement designs with cementitious base layers proposed in TRH 4 (1996). This paper demonstrates the impact of four different tyre models (including overloading) used in the mechanistic-empirical design of these pavements. In particular, the importance of adequate surface protection is demonstrated with reference to the vertical tyre contact stresses expected on these cementitious layers. The impact of the findings extends to the use (or not) of C3 - quality bases and associated surfacings on all categories of pavements carrying up to 10 million E80s. This is considered important towards the upgrading of secondary (or alternative) road pavements using cementitious stabilisers in the base layer, especially in the light of the potential future attraction of heavily loaded vehicles - with or without overloading on the tyres

A study of the influence of coarse aggregate shape characteristics on permanent deformation of asphalt mixes.

Paper presented at the 32nd Annual Southern African Transport Conference 8-11 July 2013 "Transport and Sustainable Infrastructure", CSIR International Convention Centre, Pretoria, South Africa.The effect of aggregate shape properties such as angularity, texture, sphericity, roundness, flat and elongation on the performance of asphalt mixes have not been thoroughly investigated using direct measurement techniques. This is partly because aggregates do not have regular shapes, and it is a daunting task to accurately determine these properties. In this paper, three types of aggregates are used to produce asphalt mixes in order to study the effect of coarse aggregate shape properties on the permanent deformation. A modern three-dimensional (3-D) laser scanning device available at the Council for Scientific and Industrial Research (CSIR) in South Africa was used to directly obtained shape properties of the aggregates. Permanent deformation tests were conducted in the laboratory on three different mixes produced from the aggregates to compare performance. It was found that the three asphalt mixes have different resistance to permanent formation. The aggregates with high surface texture and angularity improve resistance to permanent deformation of the asphalt mix when compared with those with more rounded or spherical shapes.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: nigel@doctech URL: http://www.doctech.co.zamv201

Analytical modelling of visco-elastic behaviour of hot-mix asphalt

Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.As part of the revision of the South African Pavement Design Method (SAPDM), laboratory testing was conducted to obtain the dynamic (Complex) modulus |E*| of hot-mix asphalt (HMA) samples. Dynamic modulus gives an indication of linear visco-elastic (LVE) behaviour of HMA materials at different temperatures and loading frequencies; and is required for computation of stresses, strains and displacements in flexible pavement analysis and design. Laboratory tests to obtain dynamic modulus are normally conducted at limited range of temperatures and loading frequencies. In order to characterize HMA mixes for pavement analysis, sigmoidal function master curves are constructed at different temperatures and loading frequencies using a time-temperature superposition principle. Instead of using the sigmoidal function, this paper presents an alternative approach for characterising the LVE behaviour of HMA materials. This approach is based on the use of three rheological models, namely, Burger’s, Huet-Sayegh and the generalised 2S2P1D. The model parameters for all three rheological models were successfully determined. The master curves were developed for all HMA mixes studied. The Cole-Cole and the Black diagrams were determined. Based on the results presented in this paper, the Huet-Sayegh and the Generalised 2S2P1D models appear to predict the LVE behaviour of HMA mixes more effectively than the Burger’s model.This paper was transferred from the original CD ROM created for this conference. The material was published using Adobe Acrobat 10.1.0 Technology. The original CD ROM was produced by Document Transformation Technologies Postal Address: PO Box 560 Irene 0062 South Africa. Tel.: +27 12 667 2074 Fax: +27 12 667 2766 E-mail: nigel@doctech URL: http://www.doctech.co.zadm201

Evaluation of selected effects of pavement riding quality on logistics costs in South Africa

The efficient operation of a country’s economy depends, among other things, on an efficient logistical system to ensure that goods can be transported efficiently between producers and users. The costs of logistics include aspects such as transport, storage, inventory, and management. Of these, the transport costs are directly influenced by the condition of the transport infrastructure. The effects of road riding quality on the costs of logistics were evaluated through analysis of data on actual truck costs (specifically, vehicle damage and maintenance) obtained from a logistics service provider as well as data on road riding quality for the routes used by the company. Analysis of the data indicated that the vehicle operating costs increased with decreasing riding quality (as would be expected). Spending adequate resources on the maintenance of routes in a country decreased vehicle fleet operating costs and ultimately the logistics costs of the country. It is recommended that the study be broadened to incorporate a larger sample of vehicles and road conditions.Imperial Logisticshttp://trb.metapress.com/home/main.mpxai201

Mechanistic-empirical compatible traffic data generation : portable weigh-in-motion versus cluster analysis

Axle load distribution factors (ALDFs) are used as one of the primary traffic data inputs for mechanistic-empirical (ME) pavement design methods for predicting the impact of varying traffic loads on pavement performance with a higher degree of accuracy than empirical methods that are solely based on equivalent single axle load (ESAL) concept. Ideally, to ensure optimal pavement structural design, site-specific traffic load spectra data—generated from weigh-in-motion (WIM) systems—should be used during the pavement design process. However, because of the limited number of available permanent WIM stations (in Texas, for example), it is not feasible to generate a statewide ALDFs database for each highway or project from permanent WIM data. In this study, two possible alternative methods, namely, the direct measurement using a portable WIM system and the cluster analysis technique, were explored for generating site-specific ME-compatible traffic data for a highway test section, namely, state highway (SH) 7 in Bryan District (Texas). The traffic data were then used for estimating pavement performance using a ME pavement design software, namely, the Texas Mechanistic-Empirical Thickness Design System (TxME). The TxME-predicted pavement performance (e.g., rutting) using the portable WIM-generated traffic input parameters closely matched with the actual field performance. Overall, the study findings indicated that the portable WIM (with proper installation and calibration) constitutes an effective means for rapidly collecting reliable site-specific ME-compatible traffic data.https://www.astm.org/DIGITAL_LIBRARY/JOURNALS/TESTEVAL/index.html2021-05-01am2020Civil Engineerin

Comparative assessment of the interlayer shear-bond strength of geogrid reinforcements in hot-mix asphalt

With the increasing use of geogrid reinforcements to mitigate reflective cracking in hot-mix asphalt (HMA) overlays, interlayer (interface) bonding has become an even more critical aspect of HMA placement/construction to mitigate delamination and debonding of the HMA overlay. To comparatively evaluate the interlayer bond strength due to the effects of the geogrid reinforcements, the shear bond strength test was conducted in this laboratory study, using unreinforced control HMA samples as the reference datum. Cylindrical HMA samples (150 mm diameter) gyratory compacted in two 75-mm lift thicknesses, with the geogrid reinforcement in-between the two lifts, were used for testing at room temperature under a monotonically shear loading rate of 5 mm/min. Emulsified asphalt was used as the interlayer tack coat and six different geogrid materials, which are polyester-based (FA) and fiberglass-based (FG), were comparatively evaluated. As theoretically expected, the control (unreinforced) HMA samples exhibited superiority followed closely by samples reinforced with polyester-based geogrids. Although comparable to the values reported in the literature, HMA samples reinforced with fiberglass-based geogrids performed the poorest with the lowest interlayer bond strengths – that is the polyester-based outperformed the fiberglass-based geogrids. Overall, the interlayer bond strength exhibited a general decreasing trend with a decrease in the geogrid mesh size (open area), increase in the geogrid strand thickness, and material grade. Thus, in as much as reflective crack mitigation is structurally desired, due diligence must be cautiously exercised when selecting the geogrid type/grade for use in HMA reinforcement to ensure sufficient interlayer bonding and minimize any potential delamination/debonding problems in service.http://www.elsevier.com/locate/conbuildmat2019-12-10hj2019Civil Engineerin