Abstract: Utilization of existing recyclable materials has always been key to more efficient and economical highway construction. Use of the foamed-asphalt (FA) technique to stabilize recycled asphalt pavement (RAP) is one strategy for an efficient use of salvaged construction materials. The main objective of this study is to investigate the potential use of FA-treated RAP as a base course material in lieu of a crushed-limestone base beneath a concrete pavement layer. Test sections were constructed at US-190 near Baton Rouge, Louisiana, and used for field evaluation of the FA RAP base. The laboratory mixture design of the FA RAP, the construction of the experimental base section, and the field evaluation of the stiffness of the FA RAP base layers using different in situ testing devices are presented. Preliminary results of both laboratory and field tests showed that the FA-treated RAP mixtures are very promising and can be used as an alternative to the traditional limestone base beneath a concrete pavement layer.

Abstract: This paper presents the results of a comprehensive laboratory investigation program on the influence of the properties of fines particles on the hydraulic characteristics of granular base-courses. ...

Abstract: Class C fly ash is a coal combustion product from lignite or subbituminous coal obtained as a result of the power generation process. In recent years, efforts have been made to incorporate self-cementing fly ash into cold in-place recycled (CIR) asphalt material to improve the structural capacity of asphalt pavement base layers. In this study, asphalt pavements in County Trunk Highway JK in Waukesha County, Wisconsin, were pulverized in place and mixed with fly ash and water to function as a base course. To evaluate the contribution of fly ash to the pavement's structural performance, nondestructive deflection tests were performed with a KUAB 2m-FWD falling weight deflectometer (FWD) on the outer wheelpath right after construction. The MICHBACK program was used to backcalculate the material properties of pavement layers from FWD measurements of deflection. The average moduli of the materials in the hot-mix asphalt layer, fly ash-stabilized base course, and subgrade were backcalculated. The structural capa...

Abstract: Reconstruction of a U.S. Department of Agriculture Forest Service campground facility in the North Dakota National Grasslands required redesign and substantial construction change because of an unstable clay subgrade. The original proposal provided for removing the old asphalt and adding additional base and a new asphalt surface. When the asphalt cement was removed, it was found that the base course had migrated into the clay subgrade, leaving the subgrade unstable. Options explored for redesign were thickened gravel base sections, lime stabilization, and geosynthetic reinforcement. The geogrid-reinforced base was selected. Design analysis consisted of two phases: (a) bearing capacity analysis for construction traffic and (b) flexible pavement analysis and design to support long-term recreation traffic. The first involved primarily Tensar design methods; the second, an empirical and mechanistic approach. Empirical methods, based on 1993 AASHTO design procedures, included Tensar methods and the recent Perkins-Michigan Department of Transportation model. The mechanistic approach used the EVERSTRESS and KENLAYER elastic layered programs. All design methods used were found beneficial and are recommended. The final flexible pavement sections constructed were dictated by the construction traffic and consisted of 2 in. of asphalt concrete on a reinforced base course ranging in thickness from 4 to 12 in. The project had to be completed in 3 weeks, so investigation and testing were limited, and the design parameters were based primarily on field dynamic cone penetrometer testing and correlations. Enforcement of the limited wheel loads became a continuous inspection problem. In addition, because of the fineness of the base aggregate produced, a separation geotextile had to be added to preclude migration of the base aggregate through the geogrid into the subgrade.

Abstract: Anhydrite (CaSO4) beds occur as a cap rock on a salt dome in Winn Parish in north Louisiana. Locally known as Winn Rock, it has been quarried for gravel for road building. It has been used as a surface course for local parish and logging roads. Stabilization of these roads with Type I portland cement followed by an overlay of asphaltic concrete sometimes resulted in heaving. The causes of heaving and possible solutions were investigated. In the laboratory, 2 in. x 4 in. molds of Winn Rock containing soil were stabilized with various cementitious mixes and cured in a 40 deg C water bath, in a 100% relative humidity room, in a sealed plastic bag at room temperature, and in air. The mixes contained 5% to 20% cementitious material. The cementitious materials were Type I portland cement, lime, and supplementary cementitious materials (SCM) such as granulated blast furnace slag (BFS), Class C fly ash, silica fume and amorphous silica. The expansion of the specimens over time was monitored. Mineralogical and microstructural analyses of the specimens were also performed over time and correlated to expansion. The Winn Rock gravel was partially weathered in the soil to gypsum, which was detected in all size fractions. The highest amount of expansion occurred in Winn Rock soil stabilized by lime cured at 40 deg C in a water bath. The magnitude of the expansion is directly proportional to the amount of Type I portland cement, the amount of available moisture, and the curing temperature. Replacement of a part of the portland cement by BFS reduced the expansion by almost an order of magnitude even at the highest moisture content. No expansion was detected when a mixture of Class C fly ash and amorphous silica was used as a partial replacement. The costs of portland cement and blast furnace slag mixtures are less than the cost of portland cement only. The addition of amorphous silica or silica fume to the cementitious mix will increase the cost significantly.

Abstract: The bedding course plays an important role in determining the serviceability of interlocking block pavement. In Japan, therefore, geotextile is commonly installed between the sand bedding course and the base course, to prevent runoff of cushion sand. The quantity of geotextile used annually has now reached about 1 million m 2 . However, there have been few studies on the beneficial effects of geotextile in keeping the bedding and base courses separated from each other and improving the pavement serviceability. The authors constructed a 30-m-long pavement test site consisting of six pavement zones with different cross-sectional dimensions in the pavement test field (circuit length: 628 m) of the Public Works Research Institute of the Ministry of Land, Infrastructure and Transportation. The pavement zones were constructed with or without geotextile having the fiber area weight of 60 g/m 2 or 130 g/m 2 , either on the granular crushed-stone base course or the permeable bituminous stabilized base course. Using a radio-operated no-man loading vehicle, a traffic simulation test of applying a 5-ton equivalent wheel load 90,000 times was performed to examine the separating effects of geotextile and the serviceability of the interlocking block pavement. The results confirmed that with either base course, geotextile helped prevent the cushion sand from migrating into the base. It was also proved that in zones with the permeable bituminous-stabilized base course, geotextile helped reduce the rutting depth and rate of block breakage, maintaining a good level of pavement serviceability. Because the fiber area weight of geotextile made no difference to the pavement serviceability, geotextile having the fiber area weight of 60 g/m 2 was

Abstract: Experiment 2 at the Louisiana Accelerated Loading Facility (ALF) site involved determining the engineering benefits of using powdered rubber modifier (PRM) in hot mix asphalt mixes. Three full scale test sections were constructed and subjected to increasing loads from the ALF. Lane 2-1 included PRM in the wearing course, lane 2-2 included PRM in the base course, and lane 2-3 was the control section. Distress and deflection measurements were performed every 25,000 applications of the ALF. Laboratory material characterizations of test lane materials were used in ABAQUS and FLEXPASS modeling studies to predict the behavior and performance of the test lanes. Comparisons of observed and predicted rutting were developed and discussed. Deflection measurements were used to develop a-values for the powdered rubber modified layers for use in pavement design. The recommended a-value for the PRM wearing course was 0.25; it was 0.45 for the PRM base.

Abstract: Hot-mix asphalt overlays are probably the most versatile way to add structural capacity, seal cracks, improve ride, enhance skid resistance, reduce noise, and improve drainage. This article describes various thin overlays, which are generally between 0.5-inch thick and 1.5 inches, and when to use them in the life of a deteriorating roadway. Smoothseal comes in two types, A and B, and is described as a good example of a thin, dense-graded overlay. It has been used in Ohio for many years. Asphalt rubber is a blend of liquid asphalt and ground tire rubber, used throughout Arizona. Michigan has developed an ultra-thin overlay as an alternative to micro-surfacing. It is similar to a sand asphalt mix.

Abstract: Asphalt pavement with semi-rigid base has been widely used in China. After more than ten years of applications, there were some performance related problems with the use of semi-rigid base. The research presented in this paper is a comparison study on the performances of semi-rigid base and asphalt-treated bose, in an effort to determine if asphalt-treated base may provide better result. In this paper, the relationship between tensile stress at the bottom Of base under traffic load is presented for the two different bases. The result shows that tensile stress at base bottom has a linear relationship with load weight The fatigue characteristics of asphalt-treated base and semi-rigid base are analysed and the results are also discussed. The analysis shows that for pavement with semi-rigid base, it is effective to use thick base to increase pavement life. For pavement with asphalt-treated base, subgrade can be strengthened to increase pavement life. Pavements with asphalt-treated base are more effective to s...

Abstract: The invention relates to a method for strengthening a road surface with an open surface structure, such as very open asphalt concrete (ZOAB), comprising of arranging a layer of asphalt concrete on the road surface, wherein the road surface respectively the asphalt concrete has a grain size distribution around an average such that an open surface structure is formed. The average of the grain size distribution in the road surface is at least substantially a factor of four greater compared to the layer, characterized by applying a layer of asphalt concrete which includes a bituminous emulsion.

Abstract: This paper presents the overall performance of hot mix asphalt mixtures containing crumb rubber modified (CRM) binders as compared to similar mixes with conventional binder under accelerated loading and to determine the best location of hot mix asphalt mixture containing CRM binder in pavement structure. Three test lanes were constructed at the Louisiana Pavement Research Facility. The first lane consisted of asphalt rubber HMA (AR-HMA) wearing course, conventional HMA binder course and conventional base course. The second test lane consisted of conventional HMA wearing course and conventional binder course, and AR-HMA base course. The third test lane was the control one and consisted of conventional mixes in the wearing course, binder course, and base course. The performance evaluation measured included rut depth and laboratory mixture performance tests. In general, the test lane containing AR-HMA mix in the wearing course showed similar rut depth, and pavement stiffness to the control test lane (with conventional mixtures), whereas, the lane containing AR-HMA mix in the base course had an improved rut resistance as compared to the control lane.

Abstract: The pressure of vibrating roller on the compacted course was simplified as cylindrical uniform load Using elastic multilayer theory, the compressive stress and tensile stress of the subbase course by vibrating compaction are calculated and analyzed The results show that there is damage possibility of semi rigid subbase in bending strength when vibrating compaction conducted on the base course

Abstract: In this paper, erosion mechanism of cement stabilized material base course of bituminous pavement is analyzed through the study of erosion development process, erosion forms and inner structure characteristic of the material. Utilizing MTS, a kind of material test system, to simulate actual situation which base course is eroded, erosion experiment of cement stabilized soil, crush stone, and gravel with different dose of cement are carried out to study factors which influence anti erosion performance of cement stabilized base course material.

Abstract: Asphalt stabilized crushed stone permeable mix, used as the base course in pavement, can significantly improve and enhance the drainage of pavement, while retaining sufficient strength and rigidity of the structure. Based on a review of studies on large pore permeable materials over the world, a method for component design of asphalt stabilized crushed stone permeable mix for pavement base is proposed in this paper, which is proven feasible by test results.

Abstract: PURPOSE: A drain cement concrete road pavement method is provided to prevent the frost damage of a base course, to heighten compressive strength and bending strength of a surface layer, to prevent the damage of a permeable hole caused by smoke, acid rain or calcium chloride and to heighten sound absorbing effect. CONSTITUTION: The drain cement concrete road pavement method comprises the steps of: paving an auxiliary base course, a stabilization layer and an impermeable base course in order; spraying water-soluble resins on the paved base course; paving a surface layer within 3 hours after paving the base course; spraying stiffener on the surface layer; and forming a lining in a gap of the surface layer by spraying resins within 3 hours after spraying stiffener on the surface layer.

Abstract: The effects of areas of road surface that have become flushed (loss of surface aggregate during hot weather) in Australia are discussed. The flushing usually extends as two ribbons along the road coinciding with vehicle wheel paths. The reasons for pavement flushing are given as excessive application rate of binder in relation to stone size, excessive prime coat being incorporated in the seal, excess binder in the underlying surface, penetration of aggregate into the base course, or primer seal covered before volatiles in primer binder have evaporated. In hot dry conditions the binder is often tacky and in wet, cool conditions it solidifies into a glassy surface. Testing of a pavement surface on two highways in central Victoria, Australia is described, along with further laboratory tests with a British Pendulum. Friction values measured were low (consistently under 40, with the lowest reading 9) and represented a hazard, particularly to heavy commercial vehicles.

Abstract: The project to widen and strengthen the 50-km Bolangir-Sonepur road in India is described. The existing road is single lane with 3.5-m pavement width. The pavement investigations that were conducted by the project coordinating consultant under the Orissa State Road Project are described. Traffic growth rates were assessed on the basis of population growth and per capita income growth. Design traffic loadings were calculated. Soil tests were conducted and expected pavement temperatures were determined. The design parameters for bitumen binder stiffness and bituminous mix stiffness and the fatigue criteria for the bituminous mix are outlined. The use of lime flyash modifications of wet mix macadam base course material and the stabilization of marginal quality natural gravel for use as sub-base were studied.

Abstract: The strength of the lime fly ash road base course materials increased a great deal when the phosphogypsum was admixed in. Their properties were modificated by the phosphogypsum. In this paper, The properties of the phosphogypsum modificating lime fly ash road base course materials such as the uncomfirmed strength, strength development, water stability and anti brushing performance were studied contracting with the lime fly ash road base course materials, the result showed that the properties of the lime fly ash road base course materials is markedly improved by phosphogypsum.

Abstract: This paper describe how, today, one of the most serious problems of asphaltic surfaced pavements containing a stabilized base course is the occurrence of transverse cracking in the stabilized base and the associated propagation of cracks to the surface, which reduces the effective life of otherwise structurally sound pavements. Compared to cement stabilized bases, Bitumen Treated Bases (BTBs) may be relatively more flexible and more resistant to fatigue cracking. However, although BTBs have been used as structural pavement layers for more than 40 years, research in this area has been very scarce. This paper summarizes the results of laboratory tests recently carried out on a BTB mix in order to assess its performance properties in relation to compaction and workability, strength, resistance to rutting and permeability.

Abstract: 水硬性粒度調整スラグ路盤材のレジリエントモジュラスを評価するために, 軸変位及び軸荷重の計測精度を向上させて, AASHTO 試験法で推奨されている繰返し載荷方法に準じて繰返し三軸圧縮試験を実施した. さらに, 西らが採用している載荷方法でも試験を行い, 既往のレジリエントモジュラスとの比較および載荷方法の違いがレジリエントモジュラスに及ぼす影響について考察した. その結果, 水硬性粒度調整スラグ路盤材のレジリエントモジュラスは, 過去の結果と同様に, 平均主応力と偏差応力に依存し養生期間が長いほど大きい値であることを確認した. さらに, 従来のようなセル外部のLVDTによる軸変位計測から算定した値はかなりの過小評価になっており, 試験法の違いの影響は非常に小さいことがわかった.

Abstract: On the basis of the non-linear(elasticity and plasticity) property of granular base, variation rules for maximum flexural tensile stress of surface course underside and semi-rigid base underside are studied with non-linear finite element solution for three types of pavements of a test road in Tonghua City of Jilin Province. Some reasonable suggestions are brought forward to semi-rigid asphalt concrete pavement with granular base in the test road. Fatigue lives of surfacing course of two types of semi-rigid asphalt concrete pavement with granular base are forcasted.

Abstract: In Japan, geotextile has been used a part of interlocking block pavement because of expecting to increase its durability. The application of geotextile for interlocking block pavement between base course and cushion sand under interlocking block prevents the cushion sand loss into the base course. The loss often causes the change of interlocking block position, damage of interlocking block, and roughness. In addition, mechanical reinforcement and water drainage are secondary functions of geotextile. Excavation surveys of interlocking block pavement that had been in use for 2-15 years after completion were carried out at five sites in order to quantitatively confirm the effects of geotextile. Research items were rutting depth, roughness, interlocking block breakage rate, residual rate of joint sand, mixing of cushion sand into base course, the quality of joint and cushion sand, and the properties of geotextile etc. The results of the excavation surveys can be summarized as follows. ! No damage to the geotextiles was observed when the pavements were cut. ! No change in the physical properties of the cushion sand was also found. ! The separation and filtering effects of the geotextiles was judged to be excellent. ! It was found that geotextile improved the long-term performance of the interlocking block pavements.

Abstract: The properties of two kinds of semi-rigid base course are studied by experiment, which include drying shrinkage and cleavage strength. On the basis of base shrinkage model, the cracking characteristics are quantitatively analyzed.

Abstract: PROBLEM TO BE SOLVED: To provide a snow melting method conducting a permeable pavement on a road in a snowfall area while being proper to a paved body, and to provide a snow melting system enabling a driving within a wide range such as a normal snow-melting driving, a preheating driving or the like in the case of a snowfall. SOLUTION: The snow melting system using a permeable paving material is composed of a paved-body structure 10 consisting of a base bedrock 13, a base course 12 and a surface course 11 installed on a roadbed 14, a heating coil 21 for melting snow mounted on the base bedrock and a coil 22 for a heat storage secured to the base section of the base bedrock 13. COPYRIGHT: (C)2004,JPO

Abstract: This paper describes how Canadian airport agencies have recently reported problems related to poor frictional properties of newly constructed (HMAC) mixes. Skid resistance of pavement surfaces is the most important component in measuring the pavement safety. Proper skid resistance is essential for safe runway operations, especially if water exists in any form. Skid resistance of pavement surface is dependent on the surface microtexture and macrotexture. Choosing good quality, polish-resistant aggregate controls microtexture and the macrotexture depends on the type and stability of mix and aggregate gradation. The main objective of this paper is to present results of the investigation of the effect of aggregate type and gradation on the safety of runway HMAC surfaces. To achieve this objective, three different mixes were obtained from Ottawa International Airport (OIA) during the rehabilitation of two taxiways. Two mixes were surface courses where limestone aggregates were used in one mix and dolomite stone aggregates were used in the other mix. The effect of aggregate gradation was evaluated through the third mix, which was a base course. The testing program included periodic friction measurements in the laboratory and in the field. The shear strength was evaluated at three different temperatures to indicate the rutting susceptibility for the mixes under study. The indirect tensile strength and moisture sensitivity tests were also evaluated. Test results showed that using dolomite stone aggregates was not a good solution in providing more safe aircraft operation. Although using these aggregates resulted in a higher initial British pendulum number (BPN), periodic measurements showed that using dolomite stones did not cause BPN to increase over that of surface course fabricated using limestone aggregates. In addition, asphalt mix made of limestone aggregates resulted in higher shear strength and better mechanical properties. The test results of the base course emphasized the role of coarser aggregate gradation to enhance the skid resistance of airfield HMAC surfaces.

Abstract: Objective of this study is to propose the structural evaluation method of concrete pavement based on back-calculation of FWD measurement data. Back-calculation has been carried out under the two conditions. One was under the condition that the elastic modulus of concrete slab was fixed and the other was varied. . As the result, it was confirmed that the back-calculation method under fixed condition was effective. And, velocity effects of the back calculated elastic moduli were examined using static loading result of the concrete slab and cyclic tri-axial testing results of mechanical stabilized base course material. Consequently, it was found that the velocity effects could be neglected by multiplying the reduction coefficient to the elastic moduli of subgrade and base course. And a reproducibility of load transfer ratio at the transverse joint was examined using this evaluation method. As the results, validity of the evaluation method proposed in this study was confirmed.

Abstract: As airports handle increasing traffic and ever-larger aircraft, it is becoming necessary to increase the durability of airport asphalt pavements. There is also demand for increased efficiency in construction procedures so as to reduce construction cost. The thick-lift construction method for asphalt concrete containing large aggregate particles makes it possible to place thicker layers than conventional methods, and is considered one possible response to these needs. The applicability of this method to airport pavement surfaces and binder courses is examined through laboratory tests and experimental construction. Through a series of investigations, it is demonstrated that large-aggregate asphalt concrete has superior resistance to deformation, mechanical properties, pavement structure, and surface characteristics as compared with asphalt concrete containing conventional aggregates.