Hot Rolled Asphalt Research Articles

Ground Penetrating Radar applied to asphaltic pavements – a study in a controlled site

ABSTRACT. The major challenges in road infrastructure studies are related to the evaluation of the road pavement quality in a practical, non-destructive, and low-cost way. Information about the thickness of the layers is fundamental to pavement repairing. In this study, the applicability of the ground penetrating radar (GPR) method in the delimitation of the pavement layer is tested at the Shallow Geophysical Test Site Applied to Engineering of Universidade Estadual de Goiás (UEG). The ground penetrating radar presents satisfactory results, identifying the top and bottom of the first five layers by the 270, 400, and 900 MHz antennas. The 2 GHz antenna was able to only delimit the top and bottom of the Hot Rolled Asphalt (HRA). The geomembrane with geotextile set and the concrete layer were not identified in the radargrams. The resolution of each antenna is 9.8 cm for 270 MHz; 6.0 cm for 400 MHz; 2.9 for 900 MHz; and 1.6 cm for 1600 MHz. Concerning layer thickness estimates, the antennas had an efficiency percentage of 83 % (270 and 1600 MHz), 83.29 % (400 MHz), and 84.40 % (900 MHz). Layer thickness estimates obtained by GPR antennas were compared with true thickness using a paired t-test (α= 0.05). No significant differences in layer thickness were observed for the GPR antennas versus the actual pavement thickness.Keywords: GPR; geosynthetics; road investigation; shallow geophysical test site; non-destructive testing.

Seasonal Signals Observed in Non-Contact Long-Term Road Texture Measurements

Texture is required on road pavements for safe vehicle braking and manoeuvres. This paper provides a unique analysis of long-term texture obtained using traffic speed condition survey (TRACS) data from 14 sites, located along a north to south transect spanning the longest highway in the UK. A total of 19 years of sensor measured texture depth (SMTD) data have been analyzed using spatial filtering techniques and compared with meteorological and traffic datasets. The results for hot rolled asphalt (HRA) surfaces reveal that changes to SMTD follow a linearly increasing trend with time. The “rate of change” is influenced by the order of magnitude of annual average daily traffic (AADT), when factored for the percentage of heavy goods vehicles. This linear trend is disrupted by environmental parameters, such as rainfall events and seasonal conditioning. In the summer, this signal is evident as a transient peak in the “rate of change” of texture greater than 0.04 mm, and in the winter as a reduction. The transient changes in texture corresponded to above average rainfall occurring in the week prior to SMTD measurement. The signal observed demonstrates an inverse pattern to the classically understood seasonal variation of skid resistance in the UK, where values are low in the summer and high in the winter. The findings demonstrate for the first time that texture measurements experience a seasonal signal, and provide compelling evidence pointing toward surface processes (such as polishing and the wetting and drying of surface contaminants) causing changes to texture that are affecting seasonal variation in skid resistance.

Predicting fatigue performance of hot mix asphalt using artificial neural networks

Developing predictive models for fatigue performance is a complex process and can depend on variables including material properties, test conditions and sample geometry. Several models have been developed in this regard; some of these are regression models and are related to mechanistic properties in addition to volumetric properties. In this work, a computational model, based on artificial neural networks (ANNs), is used to predict the fatigue performance of hot mix asphalt (HMA) tested in a dynamic shear rheometer (DSR) technique. Fatigue performance was evaluated according to three approaches: traditional, energy ratio and dissipated pseudo-strain energy. For predicting fatigue performance, two types of ANN models were developed: those dependent on test modes, that is, based on controlled test modes, and those independent of test modes, that is, irrespective of controlled test modes, using fundamental parameters, for example, stiffness modulus, phase angle and volumetric properties. In this work, limestone (L) and granite (G) aggregates were used with two binder grades (40/60 and 160/220) to prepare four mixtures with two different gradations: gap-graded hot rolled asphalt (HRA) and continuously graded dense bitumen macadam (DBM). The results revealed an excellent correlation between the predicted and experimental data. It was found that the prediction accuracy of the strain test mode was better than that of the stress test mode.

Fatigue performance of hot mix asphalt tested in controlled stress mode using dynamic shear rheometer

This study investigates the fatigue performance of hot mix asphalt (HMA) tested using a dynamic shear rheometer (DSR) under controlled stress test mode. Cylindrical DSR samples of 12 mm in diameter and 50 mm in height were prepared from a full HMA using coring technique to be used in fatigue test. Regarding fatigue evaluation, a fatigue index (FIR) has been developed based on the relationship of stress–pseudo strain hysteresis loop to be used in evaluating fatigue performance. The average values of FIR, in the relationship of FIR against normalised shear modulus, were calculated in the range of normalised shear modulus (0.85–0.20) to be used in evaluating the fatigue performance of tested samples. The FIR outcomes were in agreement in respect to the ranking order with the results from well-known approaches that have also been used for evaluating the fatigue performance, such as the energy ratio and the traditional approaches. In this study, limestone and granite aggregates were used with two binder grades: 40/60 and 160/220 to prepare four mixtures with two different gradations: gap-graded hot rolled asphalt and continuously graded dense bitumen macadam. The study demonstrated that the DSR instrument could be used to perform fatigue testing of full HMA. Also, limestone mixes showed better fatigue performance than granite.

Pengaruh Penggunaan Abu Sekam Padi sebagai Bahan Pengisi pada Campuran Hot Rolled Asphalt terhadap Sifat Uji Marshall

Rice Husk Ash (RHA) has fairly high content of SiO2 and easily obtainable. It is inexpensive since it is the residual waste of the tile or brick combustion process that is not utilized properly. RHA has the potential to be used as filler in Hot Rolled Asphalt (HRA) since it has high flexibility mixture design. The influential characteristic of RHA is that it has fine aggregate fraction. This study aims to discover the physical properties of RHA, the characteristic of the Marshall test properties, the optimum bitumen content, and the economical comparison between the RHA-mixed HRA and the conventional one using stone dust filler. The results of this study indicate that the use of the RHA is able to increase the optimum bitumen content. In terms of economical comparison, the use of RHA as filler material is much more economical than using stone dust as filler.

SENSITIVITY ANALYSIS ON FLEXIBLE ROAD PAVEMENT LIFE CYCLE COST MODEL

Sensitivity analysis is a tool used in the assessment of a model’s performance. This study examined the application of sensitivity analysis on a developed flexible pavement life cycle cost model using varying discount rate. The study area is Effurun, Uvwie Local Government Area of Delta State of Nigeria. In order to determine one of the vital geotechnical engineering properties (i.e. California Bearing Ratio) of the soil samples required for this study, soil samples were taken from the subgrade of the study area using the disturbed sampling method. The laboratory test was carried out at geotechnical laboratory in Warri and in accordance with AASTHO 1993 to determine the subgrade strength. Existing data such as maintenance records, vehicular traffic counts, material costs, discount rate and pavement design data were sourced from the Delta State Ministry of Works, Effurun. These acquired data and CBR results of 5% and 6% were used for the design of three competing flexible pavement systems and Bill of Engineering Measurements obtained. These were used for the evaluation of the Life-Cycle Costs (LCCs) using present worth cost (PWC) method; varying discount rates in MS Excel spread sheets for a design life of 20 years. Regression modeling of the three scenarios was done with sensitivity analysis carried out on the developed model. The project age was used as its independent variable, while discount rate is a secondary independent variable varied by ±4%, ±8% and ±12% of the initial discount rate of 5.4% applied with the accuracy of 95%. The coefficient of determination (R 2 ) for the Hot Rolled Asphalt (HRA), Interlocking Concrete Pavement Block (ICPB) and Do-nothing models are 0.97, 0.95 and 0.99 respectively indicating a robustness of the developed models. The graphs produced from the sensitivity analysis indicate a decrease in life cycle cost with increasing interest rate for the alternatives. These results are vital for the economic evaluation of flexible pavement and transportation systems. http://dx.doi.org/10.4314/njt.v35i2.7

The Influence of Moisture on the Performance of Polymer Fibre-Reinforced Asphalt Mixture

A number of researches have been done worldwide to evaluate the damage caused by water in bituminous pavements. The use of the retained strength ratios obtained from laboratory moisture damage tests is a useful tool in making quantitative predictions of the related damage caused by water. This study involved laboratory work on the effect of water on the performance of bituminous mixtures. Comparisons are made between the performances of Hot-rolled Asphalt (HRA) bituminous mixtures containing base bitumen of 50 pen grade to that of a polymer-fibre reinforced HRA mixture. Two types of polymer fibre were studied, namely polypropylene and polyester and these fibre were added in different concentrations in the bituminous mixtures. Changes in both the cohesive properties of the bitumen and the adhesion of the bitumen to the aggregate surface were observed as a result of exposing the bituminous mixtures to moisture. The effect of polymer fibre reinforcement in bituminous mixtures helps reduce the level of moisture damage. This was evident in the lower moisture susceptibility achieved in the polymer fibre reinforced bituminous mixtures as compared to the control mixture. The additional bitumen in the fibre reinforced mixtures also afforded an increased film thickness on the aggregate particles, thus affording additional protection of the mixtures from moisture. The reinforcement of polymer fibres in bituminous mixtures also acts to decrease the moisture sensitivity of the bitumen to aggregate bonding. This may be due to the strengthening of the wetted binder matrix that helps promote both adhesion and cohesion retention.

Life Cycle Cost Analysis (Lcca) Delivery Model for an Urban Flexible Pavement

Pavement alternative evaluation is a key aspect in decision making process in transportation system planning, design and delivery. This study examined the Life-Cycle Cost Analysis (LCCA) model for flexible road pavement infrastructure delivery in a developing economy using 1.9 km urban road in Effurun Metropolis, Uvwie Local Government Area of Delta State of Nigeria as a case study. The overview of existing knowledge, the importance and evaluation of LCCA of pavement delivery is done. The Pavement delivery and design data used for this study, which were obtained from the Office of the Ministry of Works, Effurun, Delta State of Nigeria, included soil sub-grade CBR results, water content condition, soil type and grain size distribution, the reports of route investigation, vehicular traffic counts, and previous maintenance, material and market survey reports. The pavement design data previously used for the design and procurement of urban roads in the area were used for the design of three competing pavement alternatives models, viz: Hot Rolled Asphalt (HRA), Interlocking Concrete Block Pavement (ICBP) and a third; Do-nothing scenario pavement alternative. The Bill of Engineering Measurements and Evaluation (BEME) was developed for the designed alternative to compute their Life- Cycle Costs (LCCs) using present worth cost (PWC) method with varying interest rates in MS Excel software spread sheets for a design life of 20 years. Regression modeling for the three scenarios was done with computer software’s (SPSS and MS Excel) packages. The model’s data robustness was determined and found to be between 0.95-0.99. The model’s validity and sensitivity were also carried out. The study indicates a 43.8% cost savings with the ICBP alternative over the HRA option. The Do-nothing alternative is non–aesthetical and costliest due to the maintenance cost of reinstating the road structure. The models have significance value of less than 0.001(F) respectively. The developed LCCA template and model are applicable for investment studies and decision making as well as cost effectiveness assessment of pavement and bridge delivery.

Performance of gap graded cold asphalt containing cement treated filler

Previous studies have revealed the beneficial effects of adding Ordinary Portland Cement (OPC) to Bitumen Emulsion Mixtures (BEMs). These effects were confirmed for some dense graded mixtures based on recipes currently used for hot asphalt concrete mix in the UK and being considered for usage in BEMs. On the other hand, Hot Rolled Asphalt (HRA) which is a gap graded mixture is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistance durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking.This laboratory study describes the development of novel gap-graded Cold Rolled Asphalt (CRA) by using OPC instead of conventional mineral filler. Stiffness modulus, uniaxial creep, four point load fatigue, and semi-circular bending monotonic tests were used to assess the mechanical properties while stiffness modulus ratio was determined to assess the water sensitivity of the produced mixtures.The study concluded that there is a considerable enhancement in the mechanical properties and water sensitivity of CRA containing OPC. Also, the produced cement treated gap-graded CRA shows a significant lower thermal sensitivity than conventional HRA. More interestingly, the new cement treated CRA is found to be comparable with the mechanical properties of the conventional HRA after less than 1day.

The German segmented steel roller compaction method – state-of-the-art report

Out of the European methods, the steel roller method (EN 12697-33) is preferred in Germany. A segmented roller is used, as specified in the German Standards in detail (acc. to TP Asphalt-StB, part 33; in German only). It is appropriate for laboratory compaction of any hot rolled asphalt mix types (such as asphalt concrete AC, or stone mastic asphalt SMA) either manufactured in the laboratory or in a mixing plant. And it realizes properties that are similar to those of specimen taken from the road. The segmented roller compaction method as described in the German Standards has been developed in the frame of several studies conducted at the Braunschweig Pavement Engineering Centre (see, e.g. Arand & Renken, 1990, 1999; Renken, 2001, 2002).

Superior cold rolled asphalt mixtures using supplementary cementations materials

Hot Rolled Asphalt (HRA), which is a gap-graded mixture, is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistant durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking.This paper describes a laboratory study on the production of new, superior, cold Bitumen Emulsion Mixtures (BEMs) with the same gradation used with conventional HRA mixtures and collectively incorporating different types of supplementary cementitious materials (SCM) instead of the conventional mineral filler. Accordingly, two ternary blended fillers termed as TBF-1 and TBF-2, have been blended from different SCMs and optimised to replace the conventional mineral filler.To develop the gap-graded Cold Rolled Asphalt (CRA) mixtures evaluation of stiffness modulus, creep performance and fatigue testing was used to assess the mechanical properties while stiffness modulus ratio was used to investigate the water sensitivity.The study concluded that there is a substantial improvement in the mechanical properties and water sensitivity of CRA containing TBF-1 and TBF-2. Also, the superior CRA mixtures produced showed a significant lower thermal sensitivity than conventional HRA. More remarkably, the new CRA were found to be comparable with the conventional HRA after a very short curing time (after 4h).

Laboratory studies to investigate the properties of novel cold-rolled asphalt containing cement and waste bottom ash

Cold bitumen emulsion mixtures provide valuable advantages over hot mixture asphalt in terms of economic and environmental points of view. The total energy required for mixing, transportation and laying such mixtures is less compared with the traditional hot mixtures. These laboratory studies describe the results of a new developed cold-rolled asphalt (CRA) to be comparable with the traditional hot-rolled asphalt through the addition of waste bottom ash (WBA) to the CRA containing cement as the mineral filler. The mechanical properties were assessed by stiffness modulus and uniaxial creep tests, while water sensitivity was inspected by evaluating the stiffness modulus ratio before and after samples conditioning. The experimental results have shown a significant improvement in the mechanical properties and a substantial upgrading of material resistance to water sensitivity from the addition of WBA to the cold asphalt containing cement.

A novel Cold Rolled Asphalt mixtures for heavy trafficked surface course

Hot Rolled Asphalt (HRA) surface course is a gap-graded mixture of coarse aggregate, sand, mineral filler and bitumen. The mechanical properties of the mixture are dominated by the strengthening properties of the mortar components, i.e. mineral filler, sand and bitumen. The material is extensively used for surfacing major roads in the UK because it provides a dense, impervious layer, resulting in a weather-resistant durable surface able to endure the demands of modern traffic loads and providing good resistance to fatigue cracking. However, it may experience some weakness in deformation resistance.Cold Bitumen Emulsion Mixture (CBEM) provides valuable advantages over hot asphalt mixtures in economic and environmental terms. The total energy required for mixing, transportation and laying such mixtures is lower compared with the traditional hot mixtures.This paper describes the development of a new, fast curing gap-graded Cold Rolled Asphalt (CRA) through replacement of conventional mineral filler with a Binary Blended Filler (BBF) generated from blending different percentages of two different waste fly ashes. The new CRA is found to be comparable with the traditional Hot Rolled Asphalt (HRA) after short periods of curing. The mechanical properties were assessed by stiffness modulus and uniaxial creep tests while water sensitivity was inspected by evaluating the stiffness modulus ratio before and after sample conditioning.The experimental results show a significant improvement in the mechanical properties and a substantial upgrading of material resistance to water sensitivity by the incorporation of BBF in the CRA. Moreover, the required strength i.e. 125 pen HRA stiffness modulus can be achieved after just several hours from de-moulding which represents a significant advantage when compared with the conventional reported curing times of 2–24months for the traditional CBEMs.

Development of Sustainable Cold Rolled Surface Course Asphalt Mixtures Using Waste Fly Ash and Silica Fume

AbstractThe reduction of hot asphalt mixtures for the usage and development of sustainable supplementary cold asphalt mixtures (CAMs) for the construction of road and highway surface layers is a major issue for researchers around the world. This reduction will benefit environmental impact, cost effectiveness, and energy savings. Furthermore, because CAMs comprise a remarkable portion of industrial waste (the disposal of which consumes virgin lands), they are attractive to road and highway authorities. The primary aim of this investigation is to develop new cold rolled asphalt (CRA) with the same gradation as hot rolled asphalt (HRA), which is usually used as a surface course in the U.K., and to improve its mechanical properties and durability by using waste and by-product materials as mineral fillers and additives. Waste fly ash (WFA) was used as a replacement for conventional mineral filler and a by-product silica fume (SF) was used as an additive to enhance the mechanical properties and durability of CR...

Advanced constitutive modelling of bituminous materials

Currently in the UK, the mechanical properties of bituminous (asphalt) mixtures are determined by means of a suite of tests (stiffness modulus, resistance to permanent deformation and resistance to fatigue cracking) performed by means of a pneumatic apparatus known as the Nottingham Asphalt Tester (NAT). This paper presents a methodology for an alternative experimental characterisation and modelling procedure for bituminous (asphalt) mixtures using a dynamic plasticity based constitutive model. The paper briefly describes the material response model and details the monotonic, uniaxial compression and tension testing at various temperatures and strain rates that are necessary to determine the basic model parameters. Two standard UK wearing course mixtures have been included in the testing programme comprising a continuously graded, Dense Bitumen Macadam (DBM), and a gap graded, Hot Rolled Asphalt (HRA). The uniaxial test data has been used to determine mathematical functions for the compressive and tensile strengths of the asphalt mixtures as well as functions describing their hardening and softening behaviour. Plots of the flow surface (or yield surface) have been produced for both mixtures over a range of temperatures and strain rates and the model has been successfully used to simulate the compressive response of asphalt mixtures. Once implemented in a finite element code, the constitutive model has been able to simulate the damage occurring in a flexible bituminous pavement under traffic loading.

Evaluating Four-Point Bend Fatigue of Asphalt Mix Using Image Analysis

One of the primary structural distress modes found in bituminous pavement layers is fatigue cracking, resulting from repeated application of traffic-induced stresses. The development of a four-point bending test arrangement to determine the dynamic mechanical properties of rectangular beam specimens (305345350 mm dimensions! of bituminous mixtures is discussed. This novel system allows the crack-damaged surfaces of beam specimens to be inspected and monitored digitally in situ during fatigue tests. The test fixture, which was integrated with a closed-loop servo hydraulic feedback system, incorporates a constant clamping mechanism and uses a combined displacement and loading mode of control. A series of four-point bending fatigue tests were performed on specimens of two standard Irish mixtures: a hot rolled asphalt and dense base course macadam. The digitally imaged information on fatigue cracking was used to measure the extent of damage and to characterize a linear elastic fracture mechanics model.

Effect of Mixture Compaction on Indirect Tensile Stiffness and Fatigue

When constructing laboratory samples of bituminous mixture that are intended to have the same characteristics as the in situ pavement layer, the most important factor to consider is compaction. It is widely accepted that different laboratory compaction methods produce samples with different orientations and distributions of aggregates, and different distributions and shapes of voids. The effect of different laboratory compaction procedures (namely, roller, Marshall, vibrating hammer, and gyratory techniques) on the indirect tensile stiffness and fatigue properties of two standard Irish bituminous mixtures (namely, hot-rolled asphalt and dense base coarse macadam) was investigated. The roller compaction method produced specimens of lower stiffness, similar to site compacted samples. The influence of the compaction method on the fatigue strength of asphalt mixes would appear to be mixture dependent; mixes with grading profiles that are designed for aggregate interlock were found to have higher fatigue strengths, provided the material was compacted using a method that would facilitate reorientation of the aggregates.

Wheeltracking Fatigue Simulation of Bituminous Mixtures

ABSTRACT In order to better simulate the dynamic effects of a rolling wheel travelling over an asphalt pavement, and to better understand the initiation and growth of cracks in bituminous pavement layers, a wheeltracking fatigue simulation facility was developed. This experimental facility permitted the testing of large slab specimens (305×305×50mm) using dynamic wheel loadings. The slab specimens were supported on a soft elastomeric foundation that simulated overlay behaviour on top of a weak pavement structure. Digital photography and image analysis techniques were utilised to monitor the initiation and propagation of fatigue cracks on the bottom of these slabs. Two standard Irish mixtures, a Dense Base Course Macadam (DBC) and Hot Rolled Asphalt (HRA), were evaluated with the fatigue simulation facility. Crack damage was seen to initiate on the bottom face of the slab specimen in a direction parallel to the direction of wheel travel. These cracks would interconnect to form a full width crack that propa...

Wheeltracking Fatigue Simulation of Bituminous Mixtures

ABSTRACT In order to better simulate the dynamic effects of a rolling wheel travelling over an asphalt pavement, and to better understand the initiation and growth of cracks in bituminous pavement layers, a wheeltracking fatigue simulation facility was developed. This experimental facility permitted the testing of large slab specimens (305×305×50mm) using dynamic wheel loadings. The slab specimens were supported on a soft elastomeric foundation that simulated overlay behaviour on top of a weak pavement structure. Digital photography and image analysis techniques were utilised to monitor the initiation and propagation of fatigue cracks on the bottom of these slabs. Two standard Irish mixtures, a Dense Base Course Macadam (DBC) and Hot Rolled Asphalt (HRA), were evaluated with the fatigue simulation facility. Crack damage was seen to initiate on the bottom face of the slab specimen in a direction parallel to the direction of wheel travel. These cracks would interconnect to form a full width crack that propagated through the depth of the slab. Under similar loading conditions the DBC mix had significant lower fatigue strength (two orders of magnitude).

Evaluation of asphalt fatigue properties in the laboratory

Three-point flexural fatigue tests have been carried out on prismatic specimens cut from laboratory manufactured slabs of five asphaltic materials including a hot rolled asphalt, a dense bitumen macadam and a stone mastic asphalt. Identical slabs of these materials were made to produce cylindrical specimens which were tested in the diametral fatigue test, called in the UK the indirect tensile fatigue test (ITFT). A detailed derivation is presented of the theory used to establish the feasibility of the ITFT as a fatigue test for asphaltic materials. The test results show that, at low strain levels, the fatigue lines of the five mixtures from the ITFT assume similar relative positions to those from flexural tests. However, for the same strain level, the fatigue lives measured in the ITFT are considerably shorter for all the mixtures tested. The paper highlights some of the concerns observed in connection with the ITFT procedure and their implications for fatigue testing practice.