Adhesion of asphalt mixtures

Adhesion is defined as the molecular force of attraction in the area of contact between unlike bodies of adhesive materials and substrates that acts to hold the bodies together. In the context of asphalt mixtures, adhesion is used to refer to the amount of energy required to break the adhesive bond between bitumen (bitumen-filler mastic) and aggregates. Thus, adhesive failure can be considered as displacement of bitumen (bitumen-filler) mastic from aggregates surface, which might indicates low magnitude of adhesive bond strength. Adhesion is considered as one of the main fundamental properties of asphalt mixtures, which can be correlated with quality, performance and serviceability. However, despite its significance, research on adhesion of asphalt mixtures is limited and yet there is no established testing technique and procedure that can be used to quantify the adhesive bond strength between bitumen (bitumen-filler mastic) and aggregates. Only in the past few years, some efforts have been conducted in developing testing techniques and procedures for measuring the adhesive bond strength of bitumen and aggregates. However, the developed testing techniques and procedures have not enjoyed universal success and acceptance, and not yet established. Hence, emphasis of this study is focused on the development of laboratory adhesion test method that can be used to directly measure the adhesive bond strength between bitumen (bitumen-filler mastic) and aggregates. Also, adhesive bond strength and failure characteristics of various combinations of asphalt mixture materials over wide ranges of testing conditions were evaluated in order to validate the reliability and efficiency of the developed laboratory adhesion test method. This study was divided into three parts. In Part 1, a detailed review of literature on various testing techniques and procedures used to measure the adhesive bond strength in numerous areas of scientific literature and international standards was performed, in order to assess and thus to propose the most suitable and realistic approach for development of laboratory adhesion test method for asphalt mixtures. In Part 2, the proposed adhesion test method was subjected to evaluation, mainly based on trial and error experimental approach, in order to adapt and thus to develop the criteria and procedures for test setup and apparatus, specimen preparation, testing and data analysis. The established criteria and procedures were then used for detailed evaluation in Part 3, in order to quantify the test results of various combinations of asphalt mixture materials (i.e. bitumen (bitumen-filler mastic) and aggregates) over wide ranges of thicknesses of adhesive layer of bitumen, aspect ratio of specimens, testing conditions (i.e. deformation rates and test temperatures) and conditioning procedures (dry and wet conditionings). Results of the study were subjected to comparative analysis in order to determine the effect of various variables and parameters on the test results, to propose suitable testing conditions and to validate the reliability and efficiency of the laboratory adhesion test method. Upon completion of the study, a draft protocol was developed as guiding principles in conducting the laboratory adhesion test method

Adhesion of asphalt mixtures

Adhesion is defined as the molecular force of attraction in the area of contact between unlike bodies of adhesive materials and substrates that acts to hold the bodies together. In the context of asphalt mixtures, adhesion is used to refer to the amount of energy required to break the adhesive bond between bitumen (bitumen-filler mastic) and aggregates. Thus, adhesive failure can be considered as displacement of bitumen (bitumen-filler) mastic from aggregates surface, which might indicates low magnitude of adhesive bond strength. Adhesion is considered as one of the main fundamental properties of asphalt mixtures, which can be correlated with quality, performance and serviceability. However, despite its significance, research on adhesion of asphalt mixtures is limited and yet there is no established testing technique and procedure that can be used to quantify the adhesive bond strength between bitumen (bitumen-filler mastic) and aggregates. Only in the past few years, some efforts have been conducted in developing testing techniques and procedures for measuring the adhesive bond strength of bitumen and aggregates. However, the developed testing techniques and procedures have not enjoyed universal success and acceptance, and not yet established. Hence, emphasis of this study is focused on the development of laboratory adhesion test method that can be used to directly measure the adhesive bond strength between bitumen (bitumen-filler mastic) and aggregates. Also, adhesive bond strength and failure characteristics of various combinations of asphalt mixture materials over wide ranges of testing conditions were evaluated in order to validate the reliability and efficiency of the developed laboratory adhesion test method. This study was divided into three parts. In Part 1, a detailed review of literature on various testing techniques and procedures used to measure the adhesive bond strength in numerous areas of scientific literature and international standards was performed, in order to assess and thus to propose the most suitable and realistic approach for development of laboratory adhesion test method for asphalt mixtures. In Part 2, the proposed adhesion test method was subjected to evaluation, mainly based on trial and error experimental approach, in order to adapt and thus to develop the criteria and procedures for test setup and apparatus, specimen preparation, testing and data analysis. The established criteria and procedures were then used for detailed evaluation in Part 3, in order to quantify the test results of various combinations of asphalt mixture materials (i.e. bitumen (bitumen-filler mastic) and aggregates) over wide ranges of thicknesses of adhesive layer of bitumen, aspect ratio of specimens, testing conditions (i.e. deformation rates and test temperatures) and conditioning procedures (dry and wet conditionings). Results of the study were subjected to comparative analysis in order to determine the effect of various variables and parameters on the test results, to propose suitable testing conditions and to validate the reliability and efficiency of the laboratory adhesion test method. Upon completion of the study, a draft protocol was developed as guiding principles in conducting the laboratory adhesion test method

A newly developed laboratory slab roller compactor (Turamesin): an overview

Methods of preparing test specimens in laboratories are particularly important. It also holds true in terms of compaction procedure in predicting pavement performance. The currently available laboratory compactor cannot adequately replicate field compaction conditions, especially the Stone Mastic Asphalt (SMA) mixture. The essential element of SMA mixture comprises of stones that are placed next to or on top of each other, and therefore are greatly affected by the compaction procedure. Conclusion of different studies have indicated that rolling wheel compactor, simulates properties that are closer to field compaction. Turamesin was developed as an improved method of laboratory slab roller compactor, to provide a solution for the problem of producing laboratory specimens, which would represent materials laid and compacted in the field. This paper gives an overview of Turamesin and discusses the findings of the units' first phase Pilot Study, conducted in order to provide specific information, to improve procedures for slab preparation and compaction,also determining the criteria for slab compaction and performance of Turamesin. Turamesin is able to compact, a slab area measuring; 600 mm by 500 mm, according to clients' specified thicknesses, with number of passes up to 75, within 15 minutes time period. One compacted slab could produce up to 16 cylindrical core specimens of 100 mm diameter. Turamesin has shown great potential to be adopted as standard laboratory slab compactor, for asphalt mixtures and seemes to be capable of simulating field compaction in terms of operational procedures. However, improvement of the Turamesin will need significant amount of research to develop and finalize the optimum procedures

Analysis of stone mastic asphalt (SMA) slab dimensions for evaluation of the newly developed roller compactor (Turamesin)

Stone Mastic Asphalt (SMA) is one type of asphalt mixture which is highly dependent on the method of compaction as compared to conventional Hot Mix Asphalt (HMA) mixture. A suitable laboratory compaction method which can closely simulate field compaction is evidently needed as future trend in asphalt pavement industry all over the world is gradually changing over to the SMA due to its excellent performance characteristics. This study was conducted to evaluate the SMA slab mixtures compacted using a newly developed Turamesin roller compactor, designed to cater for laboratory compaction in field simulation conditions. As the newly developed compaction device, there is a need for evaluating the compacted slab dimensions (which include length, width, and thickness), analyzing the consistency of the measured parameters to verify the homogeneity of the compacted slabs and determining the reliability of Turamesin. A total of 15 slabs from three different types of asphalt mixtures were compacted, measured, and analyzed for their consistencies in terms of length, width, and thickness. Based on study the conducted, the compacted slabs were found to have problems in terms of the improperly compacted section of about 30 mm length at both ends of the slabs and the differences in the thickness between left- and right-side of the slab which were due to unequal load distribution from the roller compactor. The results obtained from this study have led to the development of Turamesin as an improved laboratory compaction device

Preliminary investigation on establishing a new resilient modulus test approach for reduced size asphalt mixture samples smaller than 100 mm diameter

The performance evaluation of existing flexible pavements has become a priority issue for many highway maintenances engineers. To make appropriate rehabilitation and management decisions, the engineers most often rely on efficient methods for the determination of the strength of pavement layers. Resilient modulus is a very important parameter to be identified and used in pavement design. The resilient moduli of asphalt mixtures are typically measured using the indirect tension test procedure in compliance with the ASTM D4123 standard that is superseded by ASTM D7369. The standard requirement is that the prepared specimens for the tests should have a minimum height of the sample over its diameter ratio of 0.4. Generally, specimens used in the tests are either a nominal 100 mm or 150 mm in diameter with a minimum thickness over diameter ratio of 0.4. However, 100 mm diameter core specimens taken from site wearing courses with thicknesses ranging from 40 mm to 50 mm most often do not fulfil the minimum ratio of 0.4 after they are trimmed for testing. Since there was no any option, part of the binder courses had to be trimmed to make up for the minimum ratio requirement. This tends to result in inaccurate assessment of the resilient modulus values of the samples. As such, a new procedure was explored to test specimens smaller than 100 mm in diameter. This may minimize the material volume requirement from the field and also for the fabrication of smaller samples in the laboratory. Based on the available thickness of wearing course or overlay, the appropriate sizes were determined. For a two-layer system a 56.3 mm diameter was deemed necessary while a 37.5 mm diameter was observed to be appropriate for a three-layer system. Such an approach for resilient modulus test using miniature specimens of 56.3 mm and 37.5 mm in diameter has a great potential for practical relevance for the industry

Influence of polymer and aged binder on the physical and rheological properties

This research paper presents laboratory investigation on the physical and rheological properties of asphalt binde modified with Ethylene-vinyl acetate (EVA) and Aged binder in different duration. Six different concentrations (0%, 1%, 2%, 3%, 4%, and 5% by weight of base asphalt) of Ethylene-vinyl acetate (EVA) was selected to blend with 80/100 penetration grade asphalt binder. six aging duration (0 min, 45 min, 85 min, 125 min, 165 min and 205 min) by using 80/100 penetration grade asphalt binder with rolling thin film oven were selected to prepare the aged binders. The EVA modified asphalt binders as well as Aged binders was subjected to short term aging process by means of Rolling Thin Film Oven Test (RTFOT) in order to investigate the influence of the addition of EVA and aged binder in the asphalt binder properties after aging. Bituminous binder properties were investigated by both physical and rheological methods. In general, the physical test results demonstrated prominent increment in softening point; viscosity and decrement in penetration for both EVA modified asphalt binders and aged binders as compared to non-modified and non-aged binder. This study adopts a time sweep (TS) test method to study the fatigue phenomenon under control strain mode using a dynamic shear rheometer (DSR). Fatigue life of asphalt binder is defined using the traditional approach based on number of cycles required to cause to cause failure and reduction in stiffness. Temperature sweep test by using a dynamic shear rheometer (DSR) is used to predict the asphalt grade after aging and after adding Ethylene-vinyl acetate (EVA)

An overview of quantification of fatigue resistance of asphalt mixture using pre-aged binder

Asphalt binder is man’s oldest engineering material; its adhesive and waterproofing properties were known at the dawn of civilization. Asphalt paved roads have been used in the United States for about 100 years. They have been used in Europe since the 1850's. These asphalt pavements suffer from fatigue cracking and thermal cracking, aggravated by oxidation and hardening of asphalt. This negative impact of asphalt oxidation on pavement performance has not been considered adequately in pavement design. No doubt, pioneering pavement engineers soon realized that in the short-term asphalt hardened after heating, mainly due to volatilization, and, in the long term it hardened, mainly due to oxidation. Hardening is primarily associated with loss of volatile components in asphalt during the construction phase (short-term aging), and progressive oxidation of the in-place material in the field (long-term aging). Both factors cause an increase in viscosity of the asphalt and a consequent stiffening of the mixture. This may cause the mixture to become hard and brittle and susceptible to disintegration and cracking failures. Also, the products of oxidation may render the mixture less durable than the original mixture, in terms of wear resistance and moisture susceptibility. However, "aging" is not necessarily negative phenomenon, since some aging may help a mixture achieve optimum properties. Compared to research on asphalt cement and aging of asphalt mixtures, there has been little research on the blown asphalt and, to date, there is no standard test. Pavement engineers understand the need to model the effects of the blown asphalt -aggregate mixtures in structural design procedures, and while some research has addressed this need, as yet no standard procedure as emerged to address it. Part of this reason is that the process of asphalt oxidation in pavement is not well understood. The main contribution of this study is the introduction of a method to quantify fatigue damage accumulation of asphalt binders using a short-duration test procedure that can be easily implemented into current practice

Establishing stress boundaries for various loading and pavement configuration

This article is aimed to understand the relationship between stress and pavement components and finding the boundaries of the vertical and lateral stress distribution. It is carried out on four-layer pavement structure to understand the load distribution behavior through different type of materials in each layer with different resilience modulus values and different thickness. This analysis supports us to improve the pavement design accuracy and realistic, which will reduce the road maintenance cost and increase the pavement service life. Several simplifying assumptions regarding tire load applied location has been used. Therefore, 25,000 different vertical stress values in form of 125 different set of data (difference loading and pavement configuration) under five different loading conditions were analyzed using the KENPAVE software (using mechanistic empirical design method). Conclusions from the data and plot analysis show that pavement layer load distribution is affected unevenly as the effect of thickness is greater than the impact of the strength of the layer. Moreover, the results showed that there is a theoretical boundary for load distribution in the lateral direction at the bottom of the surface layer between (8 in - 14.5 in), bottom of base layer (10 in - 19.5 in) and bottom of sub-surface layer (12 in - 22 in). The stress distribution might be used as an indicator for engineers to determine the pavement behavior under an applied load

Aging and consistency characterization of bio-binders from domestic wastes

This research findings, exhibits the chemical and consistency characterization of the bio-binder produced from domestic waste (DWBO-binders) as compared with petroleum-asphalt binders. Samples of the base asphalt and DWBO modified binders were characterized by running the rotational viscosity (RV). Moreover, the elemental analysis as well as fourier transform infrared (FTIR) spectroscopy tests were utilized to validate the chemical compositions and bond initiations that caused changes in stiffness and viscosity of the asphalt modified with DWBO from those of base asphalt binders. Three factors have been found to be influenced by the use of DWBO-binder, viz; i. reduction in viscosity of asphalt binders which led to reduction of asphalt pavement construction costs by reducing mixing and compaction temperatures, ii. increasing workability, and iii. reducing greenhouse emissions and the toxic effect of binder compared with petroleum-based asphalt binders. Bio-oil from domestic waste was found to be a promising candidate as a modifier for petroleum-asphalt binder. The results of this laboratory study indicates that the inclusion of DWBO have increased the aging induces of the control asphalt binders

Chemical analysis and consistency characterization of domestic waste bio-asphalts

The objective of this paper is to characterize the chemical and consistency characterization of the bio-binder produced from domestic waste (DWBO) as compared with conventional petroleum–asphalt binder. A petroleum asphalt was modified with DWBO at 3, 6, and 9% by weight to prepare bio-binders, respectively. Samples of the DWBO-modified binders compared to base binder were tested by running the rotational viscosity (RV). Moreover, the fourier transform infrared (FTIR) spectroscopy as well as elemental analysis tests were utilized to validate the chemical compositions and bond initiations that caused changes in stiffness and viscosity of the asphalt modified with DWBO from those of base asphalt binders. This research has revealed that there are four factors to be influenced by the use of DWBO, (i) reducing greenhouse emissions and the toxic effect of binder compared with petroleum-based asphalt binders, (ii) increasing workability, (iii) reduction in viscosity of asphalt binders which led to reduction of asphalt pavement construction costs by reducing mixing and compaction temperatures, and (iv) increased the aging induces of the control asphalt binders. Bio-oil from domestic waste was found to be a promising candidate as a modifier for petroleum–asphalt binder