Papers by Author: Hamid Nikraz

Abstract: Moisture related damage is the single most significant issue facing asphalt pavements worldwide. The improvement of moisture damange resistance of asphalt concrete as a asphalt pavement surface is the way to enhance essential properties of the asphalt concrete mixture components between mix aggregate and a binder (asphalt cement) to withstand adverse effects from moisture. Moisture damage consists of two key mechanisms, the loss of adhesion between the binder and aggregate and the loss of cohesion within the asphalt contrete matrix. This research aims to investigate the adhesion mechanism through the use of the so-called rolling bottle test (RBT) to assess the binder coverage under moisture conditions. Through the use of Western Australian aggregates and Main Roads WA specific binders and adhesion agent, hydrated lime. The percentage coverage was assessed to determine the moisture sensitivity of the aggregate-binder interface. This method allows for a fundamental mechanism of moisture damage to be analysed from an inside out perspective, free of external influencing factors. The results from this study showed that different study aggregates yielded different levels of moisture damage resistance based on the results of RBTs, while the stiffer C320 binder showed greater adhesion to the both study aggregate types. The addition of hydrated lime significantly increased the percentage coverage all samples.

Abstract: This study demonstrates an assessment into the different effects of lime as a mineral filler for use in densely graded hot mix asphalt (HMA). Five percent by mass of hydrated lime and lime kiln dust (LKD) were added to an asphalt mixture as its mineral filler. A series of laboratory tests to evaluate stability and flow, resilient modulus and tensile stripping ratio with reference to a control mix (a commonly used HMA) were performed. The test results showed that mixing hydrated lime into a HMA mix could enhance superior performance of hydrated lime-HMA test samples for all tests, demonstrating no moisture susceptibility. Test samples of HMA with LKD also demonstrated moisture resistance and can offer a sustainable alternative to hydrated lime, yielding one quarter of the cost. The control mix proved to be an inadequate choice upon failing the stripping potential test and therefore deemed to be susceptible to moisture.

Abstract: This laboratory-based study investigated the performance characteristics of wet process crumb rubber modified asphalt (CRMA) with crumb rubber proportions between 0% and 20% by mass of the binder. This was to assess the viability of CRMA for use in countries where CRMA is not widely utilized as Australia and Thailand and primarily involved the resilient and dynamic modulus characteristics, which indicated that CRMA pavement has both positive and negative attributes. The results show that CRMA characterizes a reduced stiffness for high frequency loading, but with a greater elastic range.

Abstract: One of the main failure modes of a cement-stabilized road pavement base is the shrinkage cracking which could lead to negative consequences up to the failure of road pavements. The compaction time delay and cement content inherently affect to the shrinkage characteristics of the cement stabilized base course. This research aims to investigate the shrinkage characteristics with respect to the compaction time delay of a cement-stabilized base material through laboratory experiments. A series of shrinkage tests were performed on cement stabilized base samples with varying 3%, 4% and 5% of cement contents under controlled compaction delay periods varied from 0.5 hours to 1 day. The results of this study showed that shrinkage values of the study cement stabilized base increase with longer compaction time delay periods and cement contents. In addition, during an early stage (1-14 days) of shrinkage tests, shrinkage sharply increases before reaching the stage of a relatively constant rate after 14 days of testing. It would also be further notice that around 80% of the maximum shrinkage values from all tests gains in a test period between 14-21 days out of 42 days of a total shrinkage measurement period. Finally, the mathematic shrinkage model was formulated based on the test results of the study. In the model, the main factors of compaction delay time, cement content, and curing periods were used as the model variables. Shrinkage values can be predicted with a reliability of the R² value of 0.6755.

Abstract: The main objective this study is to evaluate the permanent deformation of buton rock asphalt (BRA) modified asphalt paving mixtures using dynamic creep test so that long term deformation behavior of asphalt mixtures can be characterized. The dynamic creep test was conducted on unmodified and BRA modified asphalt mixture using UTM25 machine. Asphalt cement of C170 from a regional supplier in Western Australia was used as the base asphalt binder for unmodified asphalt mixture; and BRA modified asphalt mixtures were made by substituting the base asphalt with 10, 20, and 30% (by weight of total asphalt binder) natural binder continuing granular BRA modified binder. The granular (pellets) BRA modified binder with a diameter of 7-10 mm was produced and extracted according the Australia Standard. Crushed granite was taken from a local quarry of the region; and dense graded for both unmodified and BRA modified asphalt mixture with the nominal size of 10 mm was used. The results of this analysis showed that BRA modified had a good performance as compared with unmodified asphalt mixtures, and increase in the content modified binder to 10%, 20%, and 30% resulted in decrease of the total permanent strain.

Abstract: The global development and current trends in social attitude are resulting in an increase in the amount of waste generated by society, the treatment and disposal of which are becoming a serious problem. Therefore, waste management is one of the most important aspects in ensuring sustainable development in todays world. Some of the industrial by-products, such as pulverised-fuel ash (PFA), ground granulated blast-furnace slag (GGBS) and microsilica (MS) can be used in concrete to improve its properties. In this paper the influence of various by-products on the physical properties of concrete is reviewed.

Abstract: This research is aimed at investigating the effect of elevated temperature, curing duration and curing methods on the strength recovery of lightweight concrete. Concrete specimens were subjected to elevated temperatures ranging from 300 to 600°C in a controlled heating environment. The specimens were subjected to three types of curing conditions: continuous water curing at 27°C, curing in a relative humidity of 95% at 27°C and curing in water at 60°C for three days and then curing in water at 27°C. The curing duration ranged from 7 to 56 days. The results indicated that the re-curing of concrete for the recovery of compressive strength is most effective in the temperature range from 300 to 500°C. For temperatures outside the range of 300 to 500°C, re-curing was either not effective or had limited application.

Abstract: The determination of appropriate pavement thickness using laboratory determined parameters is one of the key issues facing the road manager. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main objective of this study is to evaluate the characterization methods for fatigue performance of asphalt mixes to Western Australia road. In this study, laboratory test for indirect tensile modulus, dynamic creep, wheel tracking and aggregate gradation tests were taken to analyze each asphalt mixtures for a design traffic road. The results and analysis showed that AC20-75 asphalt mix blow is the most effective and efficient in pavement performance than the other asphalt mixes. AC14-75 was the second in rank to strengthen and durability of asphalt pavement. All asphalt mixes in this study can be used to strength and stable the overall stiffness of pavement, and modification rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.

Abstract: Modelling granular pavement materials has a significant role in the pavement design procedure. Modelling can be through an experimental or numerical approach to predict the granular behaviour during cyclic loading. The current design process in Australia is based on linear elastic analysis of layers. The analysis is performed through a well-known program CIRCLY which is applied to model bound pavement material behaviour. The KENLAYER is one of the common pavement software models used for pavement design in the United States which performs non-linear analysis for granular materials. Alternatively, a general Finite Element program such as ABAQUS can be used to model the complicated behaviour of multilayer granular materials. This study is to compare results of numerical modelling with these three programs on two sample pavement models.

Abstract: This study deals with the Austroads (2008) Guide to Pavement Technology Part 2: Pavement Structural Design on which most road pavement designs in Australia are based. Flexible pavement designs and performance predictions for pavements containing one of more bound layers derived from the mechanistic Austroads pavement design methodology and the AASHTO-2004 approach are compared for Australian conditions, with consideration of subgrade and other material properties and local design preferences. The comparison has been made through two well-known programs namely CIRCLY (5.0) and KENLAYER. The study shows that each guide has its own advantages and disadvantages in predicting stress and strain in pavement layers under different conditions. The study recommends that modifications are necessary resulting in more realistic and longer lasting pavements in Australia.