Voids Filled With Asphalt Research Articles

Evaluation of aggregate packing based on thickness distribution of asphalt binder, mastic and mortar within asphalt mixtures using multiscale methods

Aggregate packing is a key factor controlling the durability of asphalt mixtures. Considering the complex system of the aggregate structures, multiscale method was utilized by dividing asphalt mixtures into four scales, including asphalt binder, mastic, mortar and asphalt mixtures. Six asphalt mixtures with different gradation types and nominal maximum aggregate size (NMAS) were prepared and the corresponding mastics or mortars were also designed. Comprehensive image analysis methods, including high-resolution scanning, Scanning Electron Microscope (SEM), and Laser Diffraction Analyzer (LDA), were utilized to obtain the 2D images of asphalt mixtures, mortars and mastics. Then, the distribution curves of the binder within mastics, mastic within mortars, and mortar within asphalt mixtures were calculated and compared. New packing indexes were proposed, such as: expected value (Ebinder) and peak value (Pbinder) of the binder distribution at mastic scale, expected value (Emastic) and peak value (Pmastic) of the mastic distribution at mortar scale, expected value (Emortar) and peak value (Pmortar) of the mortar distribution at mixture scale. By comparing with volumetric parameters, it was found that Ebinder and Pbinder could correlate well with the volume ratio of filler to mastic. Emastic could correlate with the volume fraction of fine aggregate within the mortar, but the Pmastic may also influence by the fine aggregate gradation. The void filled with asphalt (VFA) has weak correlation with both packing indexes, Emortar and Pmortar, which indicates that VFA has limitation for evaluation of the packing properties of asphalt mixtures, and more indexes from the internal structure need to be considered.

Performance Evaluation of Styrene-Butadiene-Styrene-Modified Stone Mastic Asphalt with Basalt Fiber Using Different Compaction Methods.

Superpave gyratory compaction (SGC) and Marshall compaction methods are essentially designed according to volumetric properties. In spite of the similarity, the optimum asphalt contents (OAC) of the two methods are greatly affected by the laboratory compaction process, which would further influence their performance. This study aims to evaluate the performance of styrene-butadiene-styrene (SBS)-modified stone mastic asphalt (SMA) with basalt fiber by using SGC and Marshall compaction methods. Basalt fiber was proved to improve and strength the basic properties of SBS-asphalt according to test results of asphalt binder. The effects of SGC and Marshall compaction methods on OAC and volumetric properties, i.e., density, air voids (VA), voids in mineral aggregates (VMA), and voids filled with asphalt (VFA), were evaluated in detail. Finally, the pavement performance of asphalt mixture prepared by SGC and Marshall compaction methods were compared in order to analyze the high-temperature creep, low-temperature splitting, and moisture stability performance. Results showed that the OAC of SGC (~5.70%) was slightly lower than that of Marshall method (5.80%). Furthermore, the pavement performance of SGC specimens were improved to a certain extent compared with Marshall specimens, indicating that SGC has a better compaction effect and mechanical performance.

Multi-Objective Optimization Design and Test of Compound Diatomite and Basalt Fiber Asphalt Mixture.

This study focuses on improving the performance of asphalt mixture at low- and high- temperature and analyzing the effect of diatomite and basalt fiber on the performance of the asphalt mixture. Based on the L16(45) orthogonal experimental design (OED), the content of diatomite (D) and basalt fiber (B) and the asphalt-aggregate (A) ratio were selected as contributing factors, and each contributing factor corresponded to four levels. Bulk volume density (γf), volume of air voids (VV), voids filled with asphalt (VFA), Marshall stability (MS) and splitting strength at −10 °C (Sb) were taken as the evaluation indexes. According to the results of the orthogonal experiment, the range analysis and variance analysis were used to study the effect of the diatomite content, basalt fiber content and asphalt-aggregate ratio on the performance of the asphalt mixture, and the grey correlation grade analysis (GCGA) was used to obtain the optimal mixing scheme. Furthermore, the performance tests were conducted to evaluate the performance improvement of asphalt mixtures with diatomite and basalt fibers, and the scanning electron microscopy (SEM) tests were carried out to analyze the mechanism of diatomite and basalt fibers in asphalt mixtures. The results revealed that the addition of diatomite and basalt fiber can significantly increase the VV of asphalt mixture, and reduce γf and VFA; the optimal performance of the asphalt mixture at high- and low-temperature are achieved with 14% diatomite, 0.32% basalt fibers and 5.45% asphalt-aggregate ratio. Moreover, the porous structure of diatomite and the overlapping network of basalt fibers are the main reasons for improving the performance of asphalt mixture.

The influence of reclaimed asphalt pavement in warm mix asphalt on asphalt concrete binder course with Retona Blend 55

Reclaimed asphalt pavement (RAP) comprises removed pavement materials containing high-quality aggregates and asphalt which can be recycled as materials for new pavement construction. It is removed continually for reconstruction, resurfacing, and maintenance purposes, and if not recycled will become waste. This paper determines the influence of using different RAP percentages and asphalt content in warm mix asphalt on the Marshall test results for asphalt concrete binder course (AC-BC) using Retona Blend 55. The percentages of RAP are determined by analyzing the gradation of the existing aggregates in RAP and adding virgin aggregates so that it meets the standard gradation for AC-BC specified by the Ministry of Public Works and Housing. The RAP percentages in the asphalt mixes in this study are 35%, 45%, and 51.55% of total aggregates, while the asphalt contents are 5%, 6%, and 7% of the total mix. To determine the influence of RAP percentage and asphalt content, and to discover if there is any influence from the interaction between these two factors, the analysis is performed using a factorial design. The results of this study show that variation in RAP percentages in the mix has no significant influence on stability, flow, and Marshall quotient, but there is significant influence on void in mineral aggregates (VMA), void in mix (VIM), and void filled with asphalt (VFA). Correlations of 97.5%, 80%, and 95.1%, respectively show that increase in RAP percentage increases VMA and VIM and decreases VFA. The interaction between RAP percentage and asphalt content has no significant influence on Marshall test results.

SERAT ECENG GONDOK SEBAGAI BAHAN ALTERNATIF ADMIXTURE PADA LASTON TIPE XI SNI 03-1737-1989 DITINJAU TERHADAP NILAI-NILAI UJI MARSHALL

In Indonesia, the road construction has experienced a fairly good development. From a wide range of road constructions, flexible pavement is the most chosen one because its characteristics: easy, fast, and efficient. However, flexible pavement has many weaknesses, for example the premature damage on the road surface after some time passed by the traffic so that the road cannot reach the planned age. For that, it is done a research to add a hot asphalt mixture material that aims to improve the quality of the mixture results. The selected ingredient is natural water hyacinth. The method used is trial and error with reference of SNI 03-1737-1989. Variations used are 2%, 4%, 6%, 8% and 10% of the asphalt weight, asphalt level used is 5.72 %. Of the 5 variations of mixture used on Type XI Asphalt Concrete Layer, it is obtained the result that the water hyacinth fiber level which has the best score and meet the specifications of SNI 03-1737-1989 is on the percentage of 6% which obtained from calculation data using graphs and regression model where Marshall Stability is equal to 644,46 Kg, flow 3,39 mm, VMA (voids in the mineral aggregate) is equal to 13,83 %, VFWA (voids filled with asphalt) is equal to 65,35%, VIM (voids in the mix) is equal to 2,52 %, density of 2.31 gr/cc, and Marshall Quotient of 164.03 Kg / mm.

Fatigue Performance and Model of Polyacrylonitrile Fiber Reinforced Asphalt Mixture

Fatigue is considered a major pavement structural distress and an important part of a performance-based mix design. Currently, the fatigue model of asphalt mixture, especially the mixture incorporated with fibers, is not perfect. In this paper, the central-point bending fatigue test was conducted by constant strain mode with MTS apparatus. The fatigue performance and model of polyacrylonitrile (PAN) fiber-reinforced asphalt mixture produced with different fiber contents and asphalt contents were reported. The results indicated that the fatigue life of fiber reinforced mixture was higher than the reference one. The effects of fiber contents and asphalt contents on fatigue life were discussed. The mechanism of an optimum fiber content for the fatigue life in the fiber reinforced asphalt mixture was explained. The statistical analysis of variance (ANOVA) method and regression method were used to evaluate the effects of fiber content, strain level, and volumetric parameters, etc. on the fatigue life of an asphalt mixture. This paper presents a new fatigue performance model of a PAN fiber-reinforced asphalt mixture, including the fiber content, tensile strain, mixture initial flexural stiffness, and voids filled with asphalt (VFA). Compared to the earlier fatigue equations, the accuracy of the new fatigue model with the fiber content is improved significantly according to the statistical analysis results. Meanwhile, the model can preferably reveal the effect of fiber content, strain level, initial stiffness, and VFA on fatigue life.

ALTERNATIF PENGGUNAAN SERAT ECENG GONDOK UNTUK MENINGKATKAN INDEX PROPERTIES OF MARSHALL PADA CAMPURAN LASTON TIPE I SNI 03-1737-1989

However, flexible pavement has many disadvantages, such as early damage to the road surface after some time has passed by traffic so the road cannot reach the planned age. For this reason, a research was carried out to add hot asphalt mixture which aims to improve the quality of the mixture, the selected material is natural water hyacinth. The method used is trial and error with reference SNI 031737-1989. Variations used were 3%, 5%, and 7% of asphalt weight, the level of asphalt used was 4.48%. Of the 3 variations of the mixture used in Type I Asphalt Concrete Layer, the results obtained that the water hyacinth fiber content that has the best score and meet the specifications of SNI 03-1737- 1989 is the percentage of 7% obtained. from the calculation data using graphs and regression models where Marshall Stability is 889.73 Kg, VFWA (voids filled with asphalt) are equal to 65.97%, VIM (voids in mixtures) are equal to 1.757%, VMA (voids in mineral aggregates ) is equal to 20.30%, density 2.420 gr / cc, Flow 3.37 mm, and Marshall Quotient of 265.80 Kg / mm.Keywords : flexible pavement, water hyacinth fiber, Marshall test.

Analysis of parameters affecting asphalt mixture performance and new perspectives on the design parameters

In this paper, various factors affecting asphalt mixture performance were discussed. First, various factors were divided into four categories: material factors (MF), design factors (DF), compaction factors (CF) and volumetric factors (VF), based on how they influence the performance of the asphalt mixtures. MF referred to the properties of the aggregate, filler and binder. DF were those parameters needed to adjust in order to meet some design specifications. CF were related to the specimen compaction approach and compaction effort when molding asphalt mixture specimen. VF characterized the properties of asphalt mixtures through indices such as air voids (AV), voids in mineral aggregate (VMA), and voids filled with asphalt (VFA). The second section of the paper explored the distinctive effects from these four categories of parameters defined above, based on the study and critical review of historical literatures. Based on the discussions and analyses, the limitation of using VF in controlling asphalt mixture design results, as well as the irrationality of setting compaction effort as constant in the design process were revealed. Finally, suggestion was made that it was necessary to introduce compaction effort as DF in mixture design process, and asphalt mixtures should meet performance-based criterion and specific volumetric requirements by adjusting the MF and DF.

Evaluation of Workability and Mechanical Properties of Nonfoaming Warm Mix Asphalt Mixtures

AbstractLaboratory evaluation of mix design and mechanical properties of Warm Mix Asphalt (WMA) mixtures is necessary during the design process; consequently, the ability to quantify the compactability of WMA mixtures would be very helpful. This article presents the findings of an experimental study aimed at evaluation of the influence of mixing and compaction temperature on mix design and mechanical and workability properties of nonfoaming WMA mixtures. Asphalt mix design properties were evaluated by the Marshall method and the Superpave method. Mechanical properties such as rutting resistance were evaluated by a laboratory wheel tracking test using a Wheel Rut Tester (WRT), and the resistance to moisture-induced damage was evaluated by the Tensile Strength Ratio (TSR) approach. Workability properties were evaluated in terms of Superpave Gyratory Compactor (SGC) densification indexes using the Bahia and locking point methods. Test results indicate that WMA mixtures compacted using SGC at a lower compaction temperature of 110°C, which satisfied the Voids in Total Mixture (VTM) requirement. In order to ensure the Voids in Mineral aggregate (VMA) and Voids Filled with Asphalt (VFA) requirements of WMA mixtures, compaction temperature should be restricted to 120°C. Furthermore, WMA mixtures prepared at lower compaction temperatures exhibited higher resistance to rut deformation because of higher Traffic Densification Index (TDI) values. The energy needed to compact the WMA mixtures at lower compaction temperatures was lower due to lower Compaction Densification Index (CDI) values. WMA mixtures made with surface-saturated dry aggregates and compacted at 110°C marginally fulfilled the minimum TSR requirement because of significant reduction in the Indirect Tensile Strength (ITS) values of conditioned specimen.

Effect of aggregate contact condition on skeleton stability in asphalt mixture

ABSTRACTTo investigate the effect of aggregate contact condition on the deformation stability of asphalt mixture (DSAM), computed tomography system was used to acquire a contact parameter of aggregates – the aggregate contact index (ACI) characterising the contact characteristic for coarse aggregate. The aggregate slip tests were conducted under different test conditions . This paper investigates the relationship between ACI and slip energy index (SEI), and discusses the effects of aggregate-asphalt combined action and aggregate gradation on DSAM. The results indicate that SEI shows a good relationship with ACI. At 60 °C, SEI has the best linear correlation with the parameter ACI*VFA (Voids Filled with Asphalt), and the deformation stability has the biggest increase amplitude with the increase in ACI*VFA. In the high-temperature range (higher than 50 °C), there is a good linear relationship between SEI and ACI/VFA, and the contribution of aggregate contact to DSAM is bigger under a higher temperature. However, the action of asphalt changes to lubrication from cementation with the increase in temperature, so the growth of SEI with ACI/VFA becomes smaller. AC-13b mix has a better deformation stability than AC-13a and AC-13c mixes at 60 °C though they have the same nominal maximum aggregate size.

Analysing Properties of Asphalt Concrete Modified with Crumb Rubber Compare to Other Mixture

Several researchers have been undertake in finding alternative materials in order to be used as a modifier in asphalt mixture for the purpose of improving its properties. This research presents a study of laboratory evaluation on the performance of hot-mixed asphalt (HMA) using crumb rubber as an additive. It is noted that crumb rubber was identified to have potency as a modifier in HMA due to the elastic behavior exposed by the rubber particles, especially in reducing the rutting potential. This study fine crumb rubber Shred (2.36-0.85 mm) obtained by ambient-temperature grinding process from discarded truck tires, was used to modify asphalt concert. The fine crumb rubber with different contents, i.e. 2.5%, 5%, 7.5% and 10%, was incorporated into the mixture by using dry and wet process method in differentent temperatures. The Marshal properties, Unconfined Compressive Strength (UCS), Indirect Tensile Strength test (ITS) and Indirect Tensile Strength Modulus (ITSM), Permeability were conducted. The result showed that marshal stability, Marshal Quotient, Voids in Mix (VIM) and Voids in mineral aggregate (VMA) decreased with the increasing crumb rubber modifier. However, Marshal Flow and Void filled with asphalt (VFWA) increased when crumb rubber modifier was increased. The crumb rubber asphalt mixture result indicated has increased amount of crumb rubber in asphalt concrete mixture will decrease the Marshall Stability and permeability test shows that asphalt concrete without crumb rubber lower than AC with crumb rubber strength compare to other mixture.

Pengaruh Agregat Gabungan Terhadap Hasil Marshall Untuk HRS-WC Dan HRS-Base

The cause of the failure and damage to the roughness of the road is because the use of asphalt with high penetration value concurent with low levels mixture asphalt and the implementation of which has not been in compliance with the existing requirements, thus reduce the age of the road plan. The most commont asphalt roughness layer failure is permanent deformation AS a result of less stability and crack due to fatigue. One of the main consideration in determe the quality of asphalt mixture is the strength of the aggregate in order to endure in compliance with road planning. The issues discussed in this research is how the combined aggregate influence towards optimum levels of asphalt and asphalt mixture stability value. The research sample is asphalt penetration 60/70, coarse aggregate Awang Bangkal and Katunun-Banjarbaru Pelaihari, fine aggregate is Barito sand, filler Awang Bangkal rock burst and Tiga Roda Cement, witch total of 48 samples with levels 5-7% asphalt. Parameters of mix are stability , flow of air cavities, Voids in Mix (VIM), Void in Mineral aggeggate (VMA), Void Filled with Asphalt (VFA), Marshall Quotient (MQ), and VIM refusal to AC-WC determined from analysis of Marshall. The result achieved is the reduction in consumption levels of optimum asphalt of 0.5% for combined aggregate Awang Bangkal and Katunun Lataston mixed HRS-WC and a reduction in consumption levels of optimum asphalt of 0.2% on the mix HRS-Base on the minimum spesification 800 kg.

Influence of recycled concrete aggregate on volumetric properties of hot mix asphalt

Volumetric properties of hot mix asphalt (HMA) are necessary requirements to ensure good performance for asphalt mixtures. This research is conducted to evaluate the influence of coarse recycled concrete aggregate (CRCA) on the volumetric properties of HMA. Mix design of HMA mixture was performed for CRCA at various percentages 0%, 15%, 30%, and 60%, and the effects of the utilization of CRCA on HMA volumetric properties were evaluated. Additionally, various treatment methods were performed to evaluate the effect of various treatment types of CRCA on the HMA volumetric properties. To achieve this objective, presoaking, heat treatment followed by a short mechanical treatment were conducted. The obtained results showed that the use of the combination approach between different treatments appears to be very successful for enhancing physical properties of CRCA. The natural aggregate (NA) replacement by CRCA leads to increasing the optimum asphalt content (OAC) for the mixtures, whereas the property voids in mineral aggregates (VMA) is decreased. Compared to the mixture with 30% untreated CRCA, a little improvement and a slight increase in VMA and voids filled with asphalt (VFA) properties, respectively, were seen for mixtures with 30% treated CRCA with different treatment techniques. The CRCA addition with different proportions is very successful for both untreated and treated CRCA due to achieving all Ministry of Transportation Ontario (MTO) requirements for volumetric properties of HMA. However, CRCA treated with various treatment methods appears to be more successful than untreated CRCA application.

Analysis of volumetric properties of bituminous mixtures using cellular phones and image processing techniques

This study aims to develop the microanalysis of the bituminous mixtures using cellular phone images (CPI) and image processing techniques (IPT). A new methodology and scheme was developed for faster and accurate procedure to compute volumetric design parameters; voids in mineral aggregate (VMA), voids in total mix (VTM), and voids filled with asphalt (VFA) using CPI and IPT instead of the conventional methods. Five types of cellular phones with different camera resolutions were used to analyze the horizontal cross section (face) of hot mix asphalt slices. A cellular phone digital mapping frame for microstructure of the bituminous mixture for data collection was designed and implemented. New models for computations of volumetric design perimeters (VMA, VTM, and VFA) were developed. Results showed that the best cellular phone for microanalysis of the bituminous mixture is type D, even though it does not have the highest resolution, and the best height of capturing the images is 35 cm.

Modelling Effect of Aggregate Gradation and Bitumen Content on Marshall Properties of Asphalt Concrete

Current selection of aggregate gradation fails to explain completely the position of the aggregate gradation on a continuous scale. This study proposes a gradation index (GI) as a new parameter to determine the position of the aggregate gradation of the asphalt mixture on the continuous scale . The GI was used to develop a model of the Marshall properties. The aim of this study w as to develop a model between the GI and bitumen content of the Marshall properties that includes density, voids in the mix (VIM), voids in mineral aggregate (VMA), voids filled with asphalt (VFA), stability , and flow. The materials used were unmodified Asphalt Cement 60/70 with bitumen content variation of 4.5% to 8.0% of the mix and five variations of the aggregate gradation. Curve fitting method is used to find partial correlation factor of the aggregate gradation and the bitumen content of the Marshall properties. Multiple Polynomial Regression (MPR) models were specified to find the relationship between the GI and bitumen content of the Marshall properties. The v isualization of the relationship between the GI , bitumen content and Marshall properties used contour chart s . The results showed that the MPR determines the model of the relationship between the GI and bitumen content of the density, VIM, VMA, VFA, stability, and flow that have a very strong relationship (R 2 > 0.9) . Therefore, the model can be used to predict the Marshall properties.

Influence of volumetric property on mechanical properties of vertical vibration compacted asphalt mixture

Volumetric properties, such as volume of air voids (VV), voids filled with asphalt (VFA), and voids in mineral aggregate (VMA), strongly influence the performance of asphalt mixtures. This paper analyzes the influence of volumetric properties on the mechanical properties of the ATB-30 asphalt mixture which molds using vertical vibration compaction method (VVCM). Suggested values of volumetric properties were proposed based on the optimization of mechanical properties. Additionally, the proposed design was evaluated based on its performance in practice. Results show a 92% testing accuracy of the mechanical properties of VVCM specimens. This accuracy reveals that the vibration molding is compatible with the mechanism of the roller. High consistency was observed between the mechanical properties of the ATB-30 asphalt mixture and VV, VFA. However, the correlation between mechanical properties and VMA was poor. Hence, the suggested values of VV and VFA in the ATB-30 asphalt mixture are 2.8%–4.0% and 64%–74%, respectively, and VMA is only used as a reference with a value of at least 10.5%. Compared with the Marshall Compaction method (MCM), the Marshall stability, dynamic stability, splitting strength, and tensile strength of the ATB-30 asphalt mixture increased by 54.4%, 39.1%, 54.8%, and 53.7%, respectively, when using the design-suggested values of the VVCM design. The water stability of the asphalt mixture also improved.

Effects of Nominal Maximum Aggregate Size on the Performance of Stone Matrix Asphalt

It is well known that the performance of hot mix asphalt (HMA) in service life is closely related to a proper aggregate gradation. A laboratory study was conducted to investigate the effects of nominal maximum aggregate size (NMAS) on the performance of stone matrix asphalt (SMA). The volumetric characteristics and performance properties obtained from wheel tracking tests, permeability test, beam bending test, contabro test are compared for SMA mixes with different NMAS. The results indicated that voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) of SMA mixtures increased with a decrease of aggregate size in aggregate gradation. SMA30 had the lowest optimum asphalt content among all the mixtures. Increase of NMAS contributed to improvement of the rutting resistance of SMA mixtures. However, a decrease of NMAS showed better cracking and raveling resistance. Permeability rate of SMA was primarily affected by the air voids (AV) and break point sieve, but was also sensitive to aggregate gradation to some extent, with reduced NMAS corresponding to less permeability rate. Based on the test results, SMA5 and SMA13 are suggested to be used as a water-proof layer in bridge deck pavement, and SMA20 and SMA30 are suggested to be used as binder course in asphalt pavement, which needs to possess superior rutting resistance at high temperature.

Conceptualizing the asphalt film thickness to investigate the Superpave VMA criteria

Asphalt binder film thickness (FTb) is the key factor that is responsible for durability of asphalt mixtures. Mixtures with coarse aggregate gradations have difficulty meeting the Superpave minimum voids in mineral aggregate (VMA) criteria even though they tend to have thick asphalt films. In this study, the concept of asphalt binder film thickness (FTb) was used to investigate the Superpave VMA criteria. Superpave aggregate gradations of three nominal maximum aggregate sizes (NMAS): 9.5, 12.5 and 19.0 mm, were used. Aggregate gradations passing above, below, crossover through, humped, and through restricted zone were all considered. Superpave Gyratory Compactor test data of 126 compacted asphalt mixtures were used in the study. The current Superpave VMA criteria relate the mixture durability with VMA and set the same VMA value for mixtures with the same NMAS regardless of other parameters. However, a poor relationship was found between VMA and FTb (a durability measure) with an R2 ≅ 0.01, and yet a relatively good relationship (R2 ≅ 0.38) was found between voids filled with asphalt (VFA) and FTb although the VFA volumetric phase is part of the VMA volumetric phase in the mixture. This result was justified by the poor relationship between VFA and VMA (R2 ≅ 0.13). Despite that the effective binder content (Pbe) as a volumetric phase represents the VFA in the mixture, the relationship between FTb and Pbe was found to be more significant (higher R2) than the relationship between FTb and VFA. In this study, asphalt mixtures that did fail the Superpave VMA criteria in some cases had adequate asphalt FTb, and mixtures that passed the criteria did not necessarily have adequate FTb. In conclusion, although the current Superpave VMA criteria are significant, findings of this study support the tendency to modify the current criteria.

Development of a predictive model to estimate permeability of dense-graded asphalt mixture based on volumetrics

Asphalt mixtures with a coarser gradation typically provide greater rutting resistance due to a better structural network to resist shear, but they may present other issues, such as higher permeability. Increased permeability can facilitate water intrusion, which makes the pavement more vulnerable to moisture damage, stripping and erosion of unbound bases. Also, higher permeability promotes oxidation of asphalt binder, which may result in increased brittleness and susceptibility to cracking. The objective of this study was to develop a predictive model to estimate permeability of dense-graded asphalt mixture based on volumetrics. Eight Superpave mixtures were prepared: 9.5-mm fine and coarse graded, 12.5-mm coarse, 19-mm fine and coarse, 25-mm fine and 37.5-mm fine and coarse. Four target air void contents were defined for each mixture: 4%, 7%, 9% and 11%. Permeability tests were conducted using a falling head device according to the Florida Department of Transportation (FDOT) procedure FM 5-565. Permeability increased with air void content and nominal maximum aggregate size (NMAS); however, the effect of gradation was not conclusive as the primary control sieve point insufficiently defined gradation coarseness. In addition, voids filled with asphalt (VFA) exhibited a great correlation with permeability. Furthermore, two separate predictive models for 37.5-mm and 9.5 to 25-mm NMAS mixes were successfully developed based on regression analyses. These models provide a valuable decision tool to validate mixtures at a design stage on the basis of maximum permeability thresholds established by highway agencies.

Superpave evaluation of higher RAP contents using WMA technologies

In this study, the objective was to conduct an investigation of Superpave mix design characteristics of WMA technologies in terms of various high percentages of reclaimed asphalt pavements (RAPs). One PG 58-28 binder, two PG 64-22 binders, and two RAP sources were selected from South Carolina. In addition, three mix technologies (e.g. hot mix asphalt (HMA), foaming technology, and Evotherm additive) were employed to produce the mixtures. Meanwhile, four RAP contents of 20%, 30%, 40%, and 50% (by weight of total mixture) were utilized to blend with virgin materials. 36 Superpave mix designs were conducted to explore the volumetric characteristics of various mixtures. In this study, the results indicated that, all mixtures have an optimum asphalt content (OAC) less than 5.0%, and most of these values are close to a minimum OAC value of 4.5% set by South Carolina Department of Transportation (SCDOT). No noticeable increases at the mixing and compaction temperatures for these mixtures containing a higher percentage of RAP (i.e., over 40%) were found in this study. In addition, the voids in mineral aggregate (VMA), voids filled with asphalt (VFA), dust/asphalt ratios, and moisture susceptibility meet the requirements of SCDOT’s specifications. Therefore, these specific mix designs could be used as the guidelines for developing a set of specifications for a higher percentage of RAP in terms of warm mix asphalt technology.