Abstract: The research objectives were to investigate the feasibility of using recycled concrete aggregate (RCA) as a base course material in asphalt pavement, to evaluate the physical properties of RCA, and to develop practical and reliable guidelines and specifications. The tasks included literature review, sample collection, laboratory testing, accelerated performance testing and pavement distresses monitoring, falling weight deflectometer (FWD) test, theoretical analysis of pavement, and development of guidelines and specifications for the use of Florida RCA. Three test sections of asphalt pavement were constructed at the University of Central Florida's circular accelerated test track. Two sections of different thicknesses were constructed with RCA base and one section with limerock (LR) base. A total of 362,198 load repetitions were applied to the test sections. This is equal to 811,324 repetitions of the 18-kip (80-kN) equivalent single-axle load. The pavement distresses of rutting, cracking, and settlement were monitored during the course of the performance testing. The FWD test was performed on the pavement test sections to backcalculate the in situ resilient moduli of RCA and LR for theoretical analysis of life expectancy. The findings support the hypothesis that RCA can be used effectively as a base course when appropriate quality control techniques are used. On the basis of the information obtained, a set of specifications for the use of RCA as a base course in flexible pavements was developed.

Abstract: Recycled materials such as crushed concrete and masonry coming from demolishing buildings are widely used in the Netherlands for bases and sub-bases for road and airfield pavements. In order to be able to use these materials effectively, they should be characterised in terms of their shear strength, their resilient modulus and resistance to permanent deformation. This paper describes the main results of a large research programme that was carried out to assess these mechanical characteristics in relation to gradation, degree of compaction and composition. Also results of finite element calculations are presented which show the effect of the mechanical properties of these base course materials on the fatigue behaviour of the asphalt top layer and the permanent deformation that develops in the unbound base course. For the covering abstract see ITRD E118503.

Abstract: Several Federal Aviation Administration (FAA) specifications for base and subbase materials were evaluated with respect to frost heave and thaw weakening. The study included both unstabilized and stabilized materials. Most of the unstabilized materials allowed up to 15% fines passing the no. 200 sieve, with the exception of the crushed aggregate base, which allowed no more than 8% fines, and the sand-clay base, which allowed up to 25% fines. The Corps of Engineers (COE) frost-susceptibility criterion was used to delineate the frost susceptibility, while the time to drain a base or subbase layer was used to determine the thaw-weakening potential. The subbase (P-154) and the crushed aggregate base (P-209) met the COE frost-susceptibility criterion, but none of the materials met the COE drainage requirements. However, if the fines contents of the base or subbase were reduced to less then 3%, they did meet the criterion. The resilient modulus of cement-treated soils remained at the level found before freezing, when the cement content was greater than 5%.

Abstract: The purpose of this research was to evaluate the effectiveness of soil cement shrinkage crack mitigation techniques. The contents of this report reflect an evaluation of the construction of the test sections and a two -year evaluation of the test sections. This was accomplished through a four -part program that consisted of constructing test sections, laboratory evaluation of mater ials, structural evaluation of test sections, and crack mapping the soil cement base course and asphaltic concrete pavement. Ten test sections were constructed on LA 89, State Project number 397 -04-0004. Each test section was 1 ,000 feet long. The shrink age crack mitigation methods that were addressed included cement content, base thicknesses, fibers, interlayer, curing membrane, and curing periods. Since reflective cracks were not observed during the 1.8 year monitoring period, no conclusions can be d rawn as to the effectiveness of the different shrinkage crack mitigation methods used. However, based on the cost of construction, the sections may be ranked: 1) cement stabilized and treated base course, 2) cement stabilized base course with crack relief layer or E.A. curing membrane with sand, 3) cement stabilized base course with 0.05 percent fibers, 4) cement treated base course with 0.05 percent fibers, 5) cement stabilized base course with 0.1 percent fibers, and 6) cement treated base course with 0. 1 percent fibers.

Abstract: Salt Lake City was the site of a study which looked at the impact of utility cuts in city streets. Tests were conducted to determine the extent of the damage caused by trenching operations and non- destructive deflection testing was performed to look beyond the limits of the trenches, also referred to as determining the limits of the zone of influence. As a result of the study, the city has adopted revisions to its trench restoration details. Some of these requirements include the need for a second full depth saw cut beyond the trench wall, compact the trench backfill material and the base course to 95 per cent and thicken the base course material, and adjustments to the depth and placement of the asphalt patch.

Abstract: From the angle of fracture mechanics, the failure of pavement is analysed by starting with the interface between the pavement slab and the base course. A new concept of “transition layer”, which is formed by the infiltration of the cement mortar within pavement concrete into the base course during pavement casting, is put forward and the damage of the transition layer as the decisive cause of the static destruction and fatigue destruction of the pavement at low stress level is exposed through theoretical and experimental research. Surprisingly important knowledge and discovery about the pavement's failure mechanism are achieved. The theoretical and experimental research in laboratory indicates that the pavement-base interaction and the damage of the weak transition layer impose grave influence on the pavement failure, and through improving the condition of interface could the strength and fatigue strength (or life) be promoted, and possibly, could the thickness of the pavement be economically red...

Abstract: In a German slab track system (Feste Fahrbahn FF, system Boegl) for speeds up to 300 km/h and more different fiber optic sensors have been embedded in several levels and locations of the track system. The track system consists of prestressed precast panels of steel fiber concrete which are supported by a cat-in-situ concrete or asphalt base course. The sensors are to measure the bond behavior or the stress transfer in the track system. For that, tiny fiber-optic sensors - fiber Fabry-Perot and Bragg grating sensors - have been embedded very near to the interface of the layers. Measurements were taken on a full scale test sample (slab track panel of 6.45 m length) as well as on a real high speed track. The paper describes the measurement task and discusses aspects with regard to sensor design and prefabrication of the sensor frames as well as the embedding procedure into the concrete track. Results from static and dynamic full scale tests carried out in the testing laboratory of BAM and from measurements on a track are given.

Abstract: Fatigue tests with use of 4 Point Bending test were performed on conventional and innovative asphalt mixtures: typical asphalt concrete, high stiffness modulus asphalt concrete and stone mastic asphalt with conventional and special binders, multigrade or elastomer-bitumen. The results of fatigue testing were applied for development of fatigue characteristics of particular asphalt mixtures. Pavement design analysis was performed with design of thickness of asphalt layers and prediction of their fatigue life. It was shown that use of fatigue law developed from laboratory test results for asphalt mixture enabled to prove the efficiency of use of innovative materials. It is possible to reduce total thickness of asphalt layers when applying in base course high stiffness modulus asphalt with special binders without decrease in fatigue life.

Abstract: Perpetual pavement is a long-life asphalt pavement consisting of a three-layer hot-mix asphalt pavement intended to provide a life span of 50 years or more. The asphalt industry sought to combat the existing notion that asphalt is short lived and designed perpetual pavement to compete with portland cement concrete. The design of perpetual pavement includes flexible bottom layers that prevent distress, confining it to surface course. The three asphalt layers include a durable fatigue-resistant base layer, a rut-resistant and durable intermediate layer, and a rut-resistant, impermeable, and wear-resistant surface layer. The first placement of perpetual pavement was along a 2.5 mile stretch of I-710 in Long Beach, California.

Abstract: It is an important problem to make effective use of scrap concrete material during maintenance or reconstruetion of a cement concrete road.According the properties of regenerated concrete aggregate and the re-use as the semi-rigid base-course material stabilized by cement or lime and fly-ash,it is pionted out that the regenerated concrete aggregate has good features under the needs of the present specifications, and it is an effective way to re-use scrap concrete.

Abstract: Two typical low volume Icelandic road structures have been tested in accelerated testing by using a Heavy Vehicle Simulator (HVS). Both were surface dressed structures, one with a 20cm thick unbound base course layer and the other with the base divided into a 10cm bitumen stabilized base over 10cm unbound base. The test road structures were instrumented to estimate deflections, strains and stresses in various locations in the pavement structure. Elastic response analysis, by using a 3-D finite element (FE) technique, was carried out to simulate the tested structure and compare it with the actual measurements. The elastic stiffness moduli were entirely derived from plate load test (PLT) results. The comparison of stresses showed relatively good correlation in the subbase and the embankment. However in the base course deviation occurred between the numerical analyses and the measurements, which increased as tyre pressure increased. This was probably due to the nonlinear behaviour of the base, which was not taken into account in the linear elastic analyses. Surface deflection measurements under the wheel load on the other hand gave lower values than the numerical analyses, which it should not if nonlinear behaviour in the base took place. For the covering abstract see ITRD E118503.

Abstract: This paper presents results of a study on the development of a structural evaluation procedure for asphalt pavements with asphalt layer thicknesses less than 250 mm. The methodology does not only use the strain at the bottom of the asphalt layer and the vertical compressive strain at the top sub-base and/or subgrade as design criteria, but also the strain at the pavement surface, the compressive strain at the top of the bound road base, and the strain at the bottom of the bound road base. The load-carrying capacity of the pavement structure is expressed by the so-called Modified Structural Number, SNC, to circumvent the tedious procedure of backcalculation of layer stiffness moduli. An especially developed software tool called "QUASAR" enables easy and very quick use of the multitude of criteria to assess the structural condition of asphalt roads and to determine the required strengthening. Milling and partial milling of the asphalt layer form part of the rehabilitation measures, as well as data on rutting and development of rutting. For the covering abstract see ITRD E118503.

Abstract: The paper discusses a full-scale pavement test performed at Sandmoen near Trondheim, Norway. Two different pavements were constructed, one of them instrumented for the measurement of load responses at different depths and offsets from the pavement edge in the base and subbase layers. Results from controlled traffic and plate loading are reported in this paper.

Abstract: PROBLEM TO BE SOLVED: To provide pavement having an excellent environmental measure having the high water content of a water retention layer and being capable of inhibiting the temperature rise of a surface for a prolonged term. SOLUTION: In the pavement having the excellent environmental measure in which at least a subbase course, a base course and a surface course are formed on a subgrade, the surface course is formed in a permeable layer, and inorganic fibers are contained in the base course or the base course and the subbase course and the water retention layer is formed. In the pavement having the excellent environmental measure, a part or the whole of aggregate used for these courses is composed of the artificial aggregate of a refuse molten-slag main body while the surface course is formed in the permeable layer, rock wool is comprised to the base course and the subbase course and the first water retention layer and the second water retention layer are formed respectively, and at least a kind of a resin selected from an acrylic resin, a urethane resin and an epoxy resin and a water-based emulsion are used.

Abstract: Restrictions on land fill and environmental and political pressure led the Hong Kong Highways Department to commission a research project to investigate the potential for the use of asphalt pavement recycling in Hong Kong. The results from this project, carried out in 2000 -2002, are described. Preliminary discussions held in Hong Kong, and a global literature search, revealed that Hot In Plant Recycling (HIPR) was the most appropriate process logistically for Hong Kong's densely populated environment, with its heavily trafficked urban/rural mix of bituminous pavements primarily in need of surfacing renewal. Once this had been agreed, preliminary guidelines were developed for the selection, design and construction of asphalt pavement recycling processes for use in Hong Kong, and a laboratory test programme was then carried out to demonstrate how mixtures containing recycled asphalt pavement (RAP) could be designed to produce mixtures whose performance was equivalent to that of 100% virgin mixtures. The laboratory assessment showed that it is possible to recycle up to 50% RAP in Hong Kong asphalt concrete mixtures, and the mechanical properties of the asphalt concrete wearing course (ACWC) and base course (ACBC) materials tested were broadly comparable to those of standard mixtures without RAP manufactured to the current Hong Kong Specification. A preliminary catalogue of pavement designs was then prepared to provide a means for potential users to make use of the mechanical properties derived from the laboratory test programme, in order to carry out a flexible pavement design. Technically, HIPR was shown to be a viable, cost-effective and environmentally friendly procedure for pavement rehabilitation and new construction. Full Scale Trials are planned for a site in Hong Kong in late 2002, followed by the development of a suitable specification for more general use. The project demonstrates how a region new to asphalt recycling is tackling the various economic, environmental, political and technical issues involved. For the covering abstract see ITRD E125033.

Abstract: PURPOSE: A construction method using skid-resistant packing materials is provided to improve skid-resistance, durability and elasticity. CONSTITUTION: The construction method using skid-resistant packing materials, manufactured by the steps of crushing waste tires to have a grain size of 8 millimeters and below, gelling the surface of the crushed waste tires by heating the crushed waste tires at 200-400 degrees indirectly, heating asphalt of 0.03-0.2 weight per the crushed waste tires at 150-300 deg.C, and unifying by mixing the heated asphalt with the crushed waste tires whose surface is gelled, comprises the steps of: spraying primer(4) on a base course(3) for skid-resistant pavement; paving the manufactured skid-resistant packing materials(5) on the upper part sprayed with the primer(4); hardening the paved part of the skid-resistant materials(5) by using a roller; and spraying epoxy(6) on the surface of the hardened part.

Abstract: The effect of a reinforcement inside a flexible pavement can be investigated best by the Finite Element Method. In this paper a road structure reinforced with a steel net in the bound layers has been designed based on a three-dimensional finite element model. The aim of these FEM calculations is to investigate the effect of a reinforcement under vertical traffic load by comparing stresses and deformations of unreinforced and reinforced systems under different temperature conditions. Hereby the size and the position of the net-structure inside the construction and the total thickness of the pavement system are varied. Depending on the position of the reinforcement, different aims can be pursued. With placing the reinforcement in the upper layers rutting can be delayed whereas bearing capacity can be increased by putting the net-structure at the bottom of the asphalt base course. For the covering abstract see ITRD E118503.

Abstract: In this paper, the application of phosphogypsum to the subgrade and pavement is studied for its feasibility and mechanical performance on the basis of indoor tests and outdoor simulation tests. The tests show that under a certain construction techniques, phosphogypsum is not only a kind of the best roadbed filler but also a type of the road base course with the excellent performance,and improves to a different degree the engineering performance of the semi-rigid base course.

Abstract: PURPOSE: A pavement method for an asphalt concrete laminate with projected native rocks is provided to form a road simply, easily, economically and eco-friendly. CONSTITUTION: The pavement method for an asphalt concrete laminate with projected native rocks comprises the steps of: surfacing a road; paving a filter layer and a rubble layer on the surfaced road orderly, then paving a base course; paving an admixture composed of aggregate, binder and stiffener on the surface of the base course, then tamping; and spraying finishing materials on the surface, then curing the surface.

Abstract: Based on fatigue fracture mechanics theory, the analysis is carried out for the fatigue cracking of reinforcing asphalt concrete pavements under traffic loads by using FEM. By comparing, it is pointed out that the bonding condition between reinforcement and semi-rigid base course and the characteristics of reinforcement influence the fatigue cracking life of reinforced asphalt concrete pavements apparently. For the covering abstract see ITRD E117244.

Abstract: 本研究では, 1997年8月に建設省土木研究所 (当時) で実施したコンクリート舗装の静・繰返し載荷実験によって得られたコンクリート版のたわみ量, ひずみ, 路盤面圧力から, Westergaard モデルを用いて路盤面の変形特性に関する検討を行った. 静載荷実験結果より, Westergaard モデルによってたわみ量及び路盤面圧力を求める場合には, Vesic が示したように Boussinesq モデルとの比較結果に基づいて路盤反力係数 (K値) を修正する必要があることがわかった. また, 繰返し載荷実験結果からは, 載荷によって路盤面に残留変形が生じており, 残留変形の進行に伴いK値が低下していることが確認された.

Abstract: As part of an ongoing study on subgrade failure from accelerated pavement testing, vertical, longitudinal, and transverse stresses and strains were measured in the base course as a function of load repetitions. Both the dynamic and permanent vertical strains in the upper layer of the base course were about twice the strain in the lower part of the base. In summary, the vertical permanent strains were compressive, while the longitudinal and transverse strains were extensional in the base course. The total vertical deformation of the base was about 50% of the combined base and subgrade deformation. The permanent transverse and longitudinal strains in the middle of the base course were equal. The vertical stress in the middle of the base showed a slight increase with increasing load repetitions. Transverse stresses in the middle of the base remained constant. For the covering abstract see ITRD E118503.

Abstract: A new concept of “transition layer” is introduced in this paper. The “transition layer” is located between the surface course and the base course. The research of “transition layer”, ilom the viewpoint of fracture mechanics, shows that there exist a large number of defects and cracks in the “transition layer” before the external service loads act. Theoretical explanation and experimental research indicate that the pavement-base interface and transition layer as well as their damage impose grave influence on the pavement failure, and through improving the condition of interface could the strength and fatigue strength (or life) be promoted, According to the theoretical and experimental conclusions, the author put forward a new idea of pavement design based on the principle of fracture mechanics,

Abstract: This project was developed as a technology transfer program to develop a porous, low-strength concrete that uses large amounts of non-specification ash generated from the combustion of coal from Illinois. The Illinois-coal combustion products used for this project had a very high carbon content, over 30%. Typically, high carbon ash have little use in construction materials; however, previous project work conducted by the UWM Center for By-Products Utilization showed the feasibility of using this type of ash in po rous base construction. A properly designed and constructed porous base eliminates pumping, faulting, and cracking in pavement, thus increasing the service life of roadways, highways, and air field pavements. Porous concrete mixtures were first manufactured and tested in the UWM-CBU laboratory. These laboratory mixtures varied the amount of ash from 0% to approximately 50%. These mixtures were evaluated for fresh porous concrete properties as well as compressive strength, splitting tensile strength, flexural strength, drying shrinkage, sulfate resistance, and resistance to freezing and thawing. Hardened concrete properties were evaluated up to the age of 91 days. The laboratory mixtures were then used as the basis for mixture proportions used for field manufacturing. Pilot-scale field mixtures were manufactured at the facilities of the United Ready-Mix, Inc., Peoria, IL. The porous concrete field mixtures generated the necessary experimental and production data to determine acceptable levels of coal ash in porous base concrete mixtures for commercial production. To disseminate the results of this project to others in Illinois, a construction demonstration/technology transfer workshop was held in Peoria with cooperation from the United Ready-Mix, Inc. and the City of Peoria, Department of Public Works. The workshop consisted of a half day of lectures presenting technical results obtained for this project as well as a construction demonstration on the placement of porous base course concrete for a secti on of street in Peoria. The porous concrete mixture used for the demonstration used the highest amount of Illinois-coal ash tested for the project, over 50% by weight of total cementitious materials. Results of the project indicate that high-carbon Illinoiscoal ash may successfully be used in porous base course applications.