Porous Asphalt Mix Research Articles

Ladle furnace slag in asphalt mixes

Ladle Furnace Slag (LFS) may be used in substitution of fine aggregate (2–0.063mm), and filler (<0.063mm) in bituminous mixtures, considering its suitable particle size and hydraulic properties. From among the range of bituminous mixtures, this research is conducted on Porous Asphalt mixes (PA). Their high void ratio means they can absorb any eventual expansion of the LFS.Mechanical behavior, moisture susceptibility and durability are all tested. The results report the performance of the LFS mixtures, which showed compliance with the specifications of the relevant standards and no significant differences from those made of natural aggregates and cement.

Investigation into engineering properties and strength mechanism of grouted macadam composite materials

To further understand engineering properties of grouted macadam composite materials (GMCM) used as a surfacing layer in pavement, the mechanical properties and durability characteristics of GMCM were evaluated, and the relevant strength mechanisms were investigated at the micro level. Results indicate that GMCM has better high-temperature stability, fatigue performance and moisture stability than that of conventional asphalt mix, while it shows an acceptable decrease in low-temperature crack resistance due to the relative brittleness of hardened cement paste. The hardened cement paste also generates a spatial network crystalline lattice in asphalt mix skeleton to form a three-dimensional integral coagulation-crystalloid structure. This facilitates the asphalt mix skeleton and hardened cement paste to bear loads in unison and increase durability of the GMCM. Further, the fibre-like hydrated products of fresh cement slurry on the bitumen film surface increase the interfacial strength between bitumen and hardened cement paste due to toughening and bridging effects, which plays an important role to enhance mechanical properties and durability of GMCM. Finally, GMCM strength is from the internal friction of asphalt mix skeleton, the network structure of hardened cement paste and the adhesion between porous asphalt mix and hardened cement paste. It is concluded that GMCM can better meet the requirements of mechanical properties and durability characteristics than the conventional asphalt mix.

A Comparative Study on Properties of Malaysian Porous Asphalt Mixes with Different Bitumen Contents

Inadequate bitumen content in porous pavement construction may result in incomplete coating of aggregates which a thin bitumen film can oxidize rapidly resulting in premature failure of the pavement. This and presents the effects of porous asphalt prepared with 4.0% and up to 6.0% binder content with 0.5% increments binder. Bitumen penetration grade 60/70 and crushed granite were used in preparing the porous asphalt specimen. The porous asphalt mixes were compacted by applying 50 blows on each face using a Marshall Impact compactor. The specimens were tested for air voids, indirect tensile strength and water permeability and abrasion loss. The moisture sensitivity was assessed according to the AASHTO T283 procedures. The result shows that the increasing of bitumen content has decreased the, bulk density air voids, coefficient of permeability and abrasion loss values However, the Indirect Tensile Strength (ITS) has significantly increased and this is a good indication to resistance against moisture sensitivity. It can be concluded that the increasing of bitumen content in porous asphalt has increased the thickness of binder coating around the aggregates. This results reduction in air voids and water permeability, on the other hands it increases resistance to disintegration and ITS value which give better resistance to moisture sensitivity of porous specimens.

Performance evaluation of epoxy modified open-graded porous asphalt concrete

Open-graded porous asphalt (OGPA) mixes are applied to pavement surfaces to increase driving safety under wet conditions, and recently, to reduce tire/pavement noise. The durability of OGPA mixes, however, has been a concern since conventional OGPA mixes last typically less than ten years before major maintenance or rehabilitation is needed. This study investigates a new open-graded porous asphalt mixture that uses epoxy asphalt as binder to improve mix durability. One type of epoxy asphalt that has been successfully applied in dense-graded asphalt concrete for bridge deck paving was selected for this study. A procedure of compacting the mix into slab specimens was developed and a series of laboratory tests were conducted to evaluate the performance of the new mix, including Cantabro loss, permeability, acoustic absorption, indirect tensile, friction, shear stiffness and strength, and wheel rutting tests. Results showed superior overall performance of the epoxy modified open-graded porous asphalt mix compared to conventional open-graded porous asphalt mixes.

A Comparative Study of Anti-Stripping Additives in Porous Asphalt Mixtures

Presence of water in porous asphalt mixtures detrimentally affected the bonding between binder-aggregate interface and cohesive failure within the binder-filler mastic, making them prone to stripping which contribute to the performance and durability. This paper presents the effect of anti-stripping additives in porous asphalt mixes. In this study, the Marshall specimens were prepared using quarry dust, ordinary Portland Cement (OPC) and Pavement Modifier (PMD) as filler then mixed with 60/70 penetration grade bitumen. The specimens were measured for air voids content and coefficient of permeability and subsequently tested using indirect tensile and Cantabro tests. The moisture sensitivity of porous asphalt was determined based on the ratio of dry and conditioned specimens according to AASHTO T283. The specimens prepared with PMD showed lower air voids content, hence decrease the permeability to give a higher tensile strength and lower abrasion loss compared to specimens prepared with OPC and quarry dust. Based on the results, the PMD filler has a great potential to improve resistance to moisture damage compared to mixes with OPC and specimens prepared with quarry dust fillers.

Model of Flow Regimes in Porous Pavement and Porous Friction Courses

Porous pavements (PPs) and porous friction courses (PFCs) are increasingly recognized as viable alternatives to traditional impervious pavements. PPs and PFCs passively provide safety, hydrologic, and rainfall-runoff treatment benefits. These benefits are a result of such permeable systems providing hydraulic conveyance and filtration of particulate matter (PM) transported by runoff. With respect to hydrology, these systems reintroduce infiltration, evaporation, and storage phenomena; with respect to traffic and road safety, the systems increase skid resistance in wet conditions, reduce hydroplaning, and reduce splash-and-spray phenomena; with respect to runoff treatment, the systems function as a filter for PM and PM-bound constituents. These phenomena and the models therefore are a function of the hydrodynamics (which are not necessarily laminar) in the porous medium and commonly are characterized by the hydraulic conductivity of the porous medium. The measured hydraulic conductivity (permeability) was examined in 12 common porous asphalt mixes. A Darcian model for hydraulic conductivity in the laminar flow regime was examined, as commonly done for PPs and PFCs. However, hydrodynamic regimes in porous asphalt that extended beyond laminar flow during testing were identified for these porous mixes. Therefore, the variability of the hydraulic conductivity as a function of applied hydraulic head in a hydrodynamic regime (based on the Reynolds number) was measured and modeled. From these results, a saturated seepage model was developed; it is valid for laminar and transitional regimes. Implications for the application of standardized permeameter testing of such porous mix designs are reported.

Heterogeneous numerical modeling of asphalt concrete through use of a biphasic approach: Porous matrix/inclusions

This paper presents a numerical finite element (FE) model used to predict the dynamic modulus of porous asphalt mixes. The material considered is modeled as a biphasic medium composed of granular inclusions with linear elastic properties and a porous matrix of bituminous mastics containing a given percentage of air voids (5–6% for the purpose of this article), exhibiting linear viscoelastic behavior at small strain values. With this heterogeneous numerical model, a custom software (called “MOA”, French acronym for Random Object Modeler) developed in our laboratory has been used to generate random inclusions of various sizes and shapes in order to derive the aggregate skeleton of the particular asphalt mixture model. The chosen aggregate sizes must comply with a specific aggregate grading curve. This model is subjected to a cyclic load at a given frequency. The generalized Maxwell model has been used to determine the viscoelastic behavior of the matrix. The complex modulus and phase angle of the asphalt mixes generated from our numerical approach were compared to those obtained by Qingli Dai [1], resulting in a good agreement. This comparison leads to confirming the feasibility of the proposed heterogeneous numerical procedure. Lastly, localized stress and strain distribution results provide the basis for an interesting discussion on material design optimization in the aim of improving the mechanical properties under study.

Estimation of permeability of porous asphalt mix

A numerical estimate of the permeability of porous asphalt mix has been made taking into account the interconnectivity between the voids. Image processing techniques were employed to study the void structure by physically cutting the sample. The cutting of thin slices of porous asphalt mix (from Marshall samples) using a diamond cutter was found to be quite difficult, because of breakage and distortion of samples. Studies were, therefore, conducted on equivalent resin–aggregate samples. This equivalency was established from void ratio and void distribution considerations. Numerical analysis was performed on resin–aggregate samples for estimation of flow rate. The values obtained numerically were found to match well with the experimental results.

Application of Large-Stone Asphalt Mixes in the Base Course Maintenance of Expressway

Large stone porous asphalt mixes have well drainage ability, as well as higher modulus and durability when used as base course. Large stone porous asphalt mixes have good effect on repairing the semi-rigid base course which have longitudinal cracks. It not only can delay the reflection of cracks, but also plays the role of excluding water in structural layer owing to relatively large porosity. Deflection value of upper base's top surface decreases and deflection difference between left and right wheel track reduces after paving large-stone asphalt mixes upper base. When there are longitudinal cracks in lower base course, top surface tensile stress of upper base(large-stone asphalt mixes flexible upper base course)has significantly reduced compared with semi-rigid base course upper base. And maximum shear stress declined slightly. It can play a very well crack resistance effect when using large-stone asphalt mixes to repair broken cement stability upper base.

Relationships among Gradation Curve, Clogging Resistance, and Pore-Based Indices of Porous Asphalt Mixes

ABSTRACT When properly designed, porous asphalt functions both to make safer the driving in wet condition, and to provide hydrologic restoration while functioning as a filtration interface. This study examined the role of aggregate granulometry both on the pore-based indices of porous asphalt and on the clogging resistance. Three groups of porous asphalt gradations comprised of 12 series of samples and separated based on gradation size indices have been examined. For all samples the vertical (kv) and horizontal (kh) permeability were measured with the commensurate total void contents (e) and total porosity (n). Also clogging resistance was evaluated by measuring hydraulic conductivity before and after 1 year of exposure of the samples to dust intrusion. Marshall tests were also performed in order to control the stability of the mixes. There was a strong relationship between the permeability and the void content. For a given aggregate gradation, each increment of asphalt content increase caused a decrement in permeability and porosity. As for the clogging resistance potential, it seems to be more related to the initial permeability than to the other pore-based parameters. Results indicated that in addition to the coefficient of uniformity (U) and the total void content, a size-based granulometric index (P5·P2·Dmax) provided a relationship with vertical permeability and the total void content that were very consistent for the entire range of porous asphalt mixes. Results of this study allow the role of mix design on the permeability to be examined. These mix design results are a necessary precursor to examination of in-situ permeability after placement, and degradation of such permeability as a function of time and rainfall-runoff hydraulic and particulate loadings.

Effect of fiber types on relevant properties of porous asphalt

The research was conducted to evaluate the effects of cellulose and polyester fibers on the properties of porous asphalt mixes, using the tests of draindown, abrasion, volumetric properties, rutting, and moisture damage. Images of scanning electron microscopy and X-ray computerized tomography were adopted to identify the microstructure of the fiber and inner stone skeleton of porous asphalt. The influence of rutting parameter ( G */sin δ) of asphalt modified by different fibers on the rutting resistance of the mixes was investigated. Based upon MOHR-COULOMB theory, the cohesion and the angle of internal friction of the mixes were derived from both indirect tension and unconfined compression strength. The experimental results indicate that fibers mainly stabilize asphalt binder and thicken asphalt film around aggregates. Furthermore, they result in the improved mechanical strength of porous asphalt mixes at high temperature slightly. From comparison analysis, cellulose fibers appear to perform better than polyester fibers in porous asphalt mixes.

Laboratory Measurements and Analysis of Clogging Mechanism of Porous Asphalt Mixes

Abstract A laboratory test to assess the clogging potentials of porous asphalt mixes is useful as part of a rational design procedure of these mixes for the construction of pavement surface friction courses. Following an earlier successful attempt in inducing clogging in porous specimens in the laboratory, this paper describes a project studying the clogging potentials for porous asphalt pavements of different thicknesses under simulated field conditions. The clogging potentials were studied through the monitoring of the deterioration of the permeabilities of the laboratory specimens, made possible by a new falling-head permeameter that measures three-dimensional flow. An attempt was also made to relate the results thus obtained to a simple theoretical model suggested by Giroud for geotextiles. It was found that there was a fairly good comparison between experimental results and theory.

A New Apparatus for Measuring the Drainage Properties of Porous Asphalt Mixes

Abstract A new apparatus is designed to measure the permeability of porous asphalt road mixes under laboratory conditions. This apparatus works on the falling head principle, from which the falling head with time through a porous specimen is measured with a pracise pressure transducer at very close time intervals (10 readings/s). Using the falling head data, she specific discharge through the specimen can be computed and the penneability of the material obtained from the velocity versus hydraulic gradient relationship. Tests on unbound specimens made with glass spheres showed excellent agreement with constant head test results. The influence of specimen diameter and thickness in relation to particle size is examined, and recommendation for appropriate specimen size proposed. Tests with three types of common porous asphalt mixes were conducted and it is demonstrated that specification of void content alone is not adequate for describing the drainage property of a porous mix.