Stabilized Base Course Research Articles

Sustainable development of pavement base stabilization using future road base material (FROBM)

Sustainable road construction has emerged as a critical issue in assessing natural resources and urban development. With the rapid expansion of pavement networks to meet growing traffic demands, road base construction relies heavily on the consumption of natural aggregates and Ordinary Portland Cement (OPC) through the cement-treated base (CTB) technique. This practice contributes to the global warming and greenhouse gas (GHG) emissions associated with road construction. This study investigated a novel road base material, Future Road Base Material (FROBM), which emphasizes both eco-friendliness and economic advantages. Fine crushed rock (FCR) served as the parent aggregate and was modified with a chemical binder comprising 4% of the FCR weight. The proposed sustainable cementitious material, functioning as a non-OPC binder, incorporated fly ash and hydrated limestone as pozzolanic materials, along with sodium hydroxide (NaOH) as an alkali additive. An asphalt emulsion (AE) was employed as a special additive to enhance crucial pavement engineering properties. Through life cycle analysis (LCA), the construction activities and material acquisition of each stabilized base technique were evaluated in terms of project costs and carbon footprints. The non-OPC binder offered sufficient compressive strength for a stabilized base course. Furthermore, the addition of AE improved the elastic modulus and modulus of rupture of the non-OPC binder-stabilized mixture. Utilizing a non-OPC binder and AE in the base layer provides advantages in terms of construction cost and environmental impact. Although the costs increased slightly, the GHG emissions were reduced by approximately 30% compared to conventional base materials, with equivalent functionality and service life for road construction. The proposed stabilizing agent reduced the operational processes and demand for natural aggregates compared with the unbound FCR base course. Road-base stabilization using a non-OPC binder and AE represents an innovative approach to mitigate waste in coal mining and power plant industries by transitioning to a cleaner product. The concept of the FROBM serves as a valuable guideline for the development of future sustainable pavement materials.

Evaluation of Mechanical Performance of Asphalt Emulsion Stabilized Base Course Composed of Reclaimed Asphalt Pavement and Asphaltenes

Abstract Reclaimed asphalt pavement (RAP) is a material that is produced by milling old asphalt pavement that can be mixed with virgin asphalt binder and aggregates to fabricate a recycled asphalt mixture. Using RAP in pavement structure can promote sustainability and reduce construction costs. In this study, asphaltenes, which is a waste material derived from oil sands deasphalting operation, was added as a modifier to recycled mixtures composed of different contents of RAP. A proctor test was conducted to determine the optimum fluid contents. Mix designs were performed for mixtures with 50 %, 75 %, and 100 % RAP with asphalt emulsion and different asphaltenes contents. Mechanical properties of the modified mixtures were evaluated by conducting the indirect tensile strength (ITS) test, creep compliance and strength test, indirect tensile asphalt cracking test (IDEAL-CT), and Hamburg wheel tracking test. The optimum emulsion content was determined to be 1.5 % based on sample performance using the ITS test. The results indicate that asphaltenes improves the strength up to the design-specified limits. The asphaltenes-modified samples show lower creep compliance and fracture energy (FE) values than the unmodified sample, indicating these samples are potentially more prone to cracking. Further, statistical analysis shows the difference in FE is significant at the lowest testing temperatures (−20°C). Asphaltenes-modified mixtures have greater cracking resistance at the intermediate temperature (25°C) and rutting performance at high temperature (40°C) than the unmodified mixture. However, based on FE and rutting resistance index, the improvements are not significant. Overall, the 100 % RAP mix with 1 % asphaltenes had the best tensile strength, cracking resistance, rutting resistance, and low temperature properties compared to other modified mixes.

Investigation of the performance of cement-stabilized magnesium slag as a road base material

The harmless, resource-saving, and large-scale utilization of magnesium slag (MS) from industrial waste has become an important topic for road research. The use of MS as a substitute for aggregate is a practical and efficient way to dispose of it. However, there is a lack of systematic research on how to standardize its use in road construction. The objective of this study was to investigate the applicability and feasibility of using MS for cement stabilized base course materials. The influence of different cement dosages, curing age, and gradation on the strength, stiffness and stability of cement-stabilized magnesium slag mixture (CMSM) was investigated, and the actual road performance of CMSM was analyzed by paving a test road. The results showed that the mechanical properties of the CMSM met the requirements for road base courses under medium-to-light traffic when the cement dosage was above 5%. The unconfined compressive strength loss rate of the CMSM was less than 13% for an immersion time of 1 to 7 days, and after 5 freeze–thaw cycles, the frost resistance coefficient of the CMSM was more than 85%. The performance of the CMSM was most affected by cement dosage and curing age, closely followed by mixture grading type. MS can enhance the development of the pozzolanic reaction, resulting in improved strength and compactness of CMSM. Overall, CMSM exhibited exceptional road performance and could reduce aggregate costs by 25% to 35%. The use of MS as an aggregate for road base courses offers a sustainable solution that not only maximizes the use of solid wastes, but also avoids the potential safety hazards and environmental pollution caused by improper disposal and stockpiling of MS.

Research on Water-saving, Moisture-keeping and Curing Technology of Cement Stabilized Base Course of Highway

The cement stabilized macadam base has excellent road performance and economy, and it is widely used. However, cement stabilized macadam also has some shortcomings such as poor anti-scour ability and insufficient frost resistance. To solve this problem, this study uses Scanning Electron Microscope (SEM) to analyze the micro-morphology of the specimen surface under four curing methods, namely moisturizing film, sack, polyethylene film and curing room, explaining the mechanism of curing methods affecting the anti-scour performance of cement stabilized macadam. Through the experimental study of anti-scour performance, it was found that the water-saving and moisturizing film was the closest to the experimental condition of curing in the curing room; the scour rates of the specimens of health-preserving sacks and polyethylene films were both high, and they were respectively 12.1g and 16.7g at 15m; through the experimental study of frost resistance, it was found that these curing methods had little influence on the frost resistance of cement stabilized macadam, and the ratio of compressive strength exceeded 0.6%.

Evaluation of a Concrete Slab Track with Debonding at the Interface between Track Concrete Layer and Hydraulically Stabilized Base Course Using Multi-Channel Impact-Echo Testing.

Multi-channel Impact-echo (IE) testing was used to evaluate debonding defects at the interface between track concrete layer, TCL, and hydraulically stabilized base course, HSB, in a real scale mockup model of concrete slab tracks for Korea high-speed railway (KHSR) system. The mockup model includes three debonding defects that were fabricated by inserting three 400 mm by 400 mm (length and width) thin plastic foam boards with three different thicknesses of 5 mm, 10 mm, and 15 mm, before casting concrete in TCL. Multi-channel IE signals obtained over solid concrete and debonding defects were reduced to three critical IE testing parameters (the velocity of concrete, peak frequency, and Q factor). Bilinear classification models were used to evaluate the individual and a combination of the characteristic parameters. It was demonstrated that the best evaluation performance was obtained by using average peak frequency or the combination of average peak frequency and average Q factor, obtained by eight accelerometers in the multi-channel IE device. The results and discussion in this study would improve the understanding of characteristics of multiple IE testing parameters in concrete slab tracks and provide a fundamental basis to develop an effective prediction model of non-destructive evaluation for debonding defects at the interface between TCL and HSB in concrete slab tracks.

Performance Evaluation of Stabilized Base Course using Asphalt Emulsion and Asphaltenes Derived from Alberta Oil Sands

Stabilization of the pavement base course using asphalt emulsion is one of the strategies that improves the layer’s strength and, consequently, enhances the pavement performance. In this study, to improve the performance of the asphalt-emulsion-stabilized base course, asphaltenes derived from Alberta oil sands bitumen are added to the mix. Asphaltenes are a byproduct of the deasphalting process of oil sand bitumen and have no significant value in the asphalt industry. The modified mixes are prepared by adding different amounts of asphaltenes in powder form to the mix at ambient temperatures. Marshall stability and indirect tensile strength of the mixtures are evaluated using different contents of asphalt emulsion and asphaltenes. The low-temperature performance properties of the selected mixtures are investigated using an indirect tensile test and for the high-temperature properties a wheel-tracking test is conducted. The results of this study indicate that the addition of asphaltenes to the emulsion-stabilized mix significantly improves rutting resistance, with a slight increase in moisture sensitivity. However, the indirect tensile test results also reveal that modified mixes are slightly more prone to low-temperature cracking than are unmodified ones.

Laboratory evaluation of stabilized base course using asphalt emulsion and asphaltenes derived from Alberta oil sands

Permanent deformation and moisture sensitivity are the two main challenges with the performance of asphalt emulsion-stabilized base courses. This study investigates the application of asphaltenes as a waste material derived from Alberta oil-sands bitumen in improving stabilized base course mechanical properties. Hence, 1% to 3% of asphaltenes by total weight of mix is added to a granular aggregate stabilized with asphalt emulsion. The impact of asphaltenes on the tensile strength, moisture susceptibility, and rutting performance of the modified mixtures is investigated. The asphaltenes-modified base courses have higher tensile strength and rutting resistance, while their moisture susceptibility is slightly lower than the control mix.

Verifying Moisture Damage Impact in Asphalt Concrete with the Aid of Nondestructive Test NDT

One of the major concerns of pavement durability is its susceptibility to moisture damage. In this investigation, non-destructive test NDT has been implemented to detect the moisture damage issue. Asphalt concrete specimens were prepared using the traditional Marshall method for wearing, binder and asphalt stabilized base course. Specimens were traversed by ultrasound pulse velocity before and after practicing the moisture damage procedure. The variation of dynamic and elastic modulus before and after the moisture damage was considered and related to tensile strength ratio TSR. It was noted that the pulse velocity decline by (11, 11.2 and 16.4) % and the dynamic modulus declines by (28, 6.6 and 28.5) % for asphalt concrete wearing, binder and base courses respectively after moisture damage. The elastic modulus exhibits no significant variation after moisture damage for wearing course while it declines by (9 and 11.7) % for binder and base courses respectively after moisture damage. It was concluded that the elastic and dynamic moduli were unable to clearly distinguish the impact of moisture damage, whereas the Seismic modulus calculated from the Ultrasonic Pulse Velocity test was effective in distinguishing such impact. The linear equation obtained with good coefficient of determination can explain 74 % of the variation in the seismic modulus after moisture damage.

Experiment on Gyratory Compaction of Cement Stabilized Base Course Materials

Experiment on Gyratory Compaction of Cement Stabilized Base Course Materials

POTENTIAL USE OF CINDER GRAVEL AS AN ALTERNATIVE BASE COURSE MATERIAL THROUGH BLENDING WITH CRUSHED STONE AGGREGATE AND CEMENT TREATMENT

Cinder gravels are pyroclastic materials associated with recent volcanic activity which occur in characteristically straight sided cone shaped hills. The aim of this study was to use this marginal material which is abundantly available in many parts of Ethiopia by modifying their properties through mechanical blending and chemical stabilization. Results of physical and mechanical test conducted on cinder gravel samples prove their marginality to be used as base course materials especially for highly trafficked roads. An experimental investigation were carried by blending cinder gravels with conventional crushed stone bases course material, Crushed Stone Aggregate (CSA), in proportions of cinder/ Crushed Stone Aggregate (CSA) (10/90, 20/80, 30/70, 40/60 and 50/50) and treating with 6. 8 and 10% of cement. According to results of sieve analysis, Aggregate crushing value (ACV), flakiness index and California Bearing Ratio (CBR), 30% of Crushed Stone Aggregate (CSA) can be replaced by cinder gravels for use as Fresh, crushed rock (GB1) material and for cement treated cinder gravels adding 6% and 8% cement make them suitable for use as Stabilized base course (CB2) and (CB1) base course materials respectively, referring to their 14 day compressive strength as determined by Unified compressive strength test(UCS) test.

Shrinkage Characteristics and Modeling of Cement Stabilized Road Pavement Bases: A Compaction Delay Investigation

One of the main failure modes of a cement-stabilized road pavement base is the shrinkage cracking which could lead to negative consequences up to the failure of road pavements. The compaction time delay and cement content inherently affect to the shrinkage characteristics of the cement stabilized base course. This research aims to investigate the shrinkage characteristics with respect to the compaction time delay of a cement-stabilized base material through laboratory experiments. A series of shrinkage tests were performed on cement stabilized base samples with varying 3%, 4% and 5% of cement contents under controlled compaction delay periods varied from 0.5 hours to 1 day. The results of this study showed that shrinkage values of the study cement stabilized base increase with longer compaction time delay periods and cement contents. In addition, during an early stage (1-14 days) of shrinkage tests, shrinkage sharply increases before reaching the stage of a relatively constant rate after 14 days of testing. It would also be further notice that around 80% of the maximum shrinkage values from all tests gains in a test period between 14-21 days out of 42 days of a total shrinkage measurement period. Finally, the mathematic shrinkage model was formulated based on the test results of the study. In the model, the main factors of compaction delay time, cement content, and curing periods were used as the model variables. Shrinkage values can be predicted with a reliability of the R2 value of 0.6755.

Degradation reliability modeling of stabilized base course materials based on a modulus decrement process

The dynamic elastic modulus of stabilized base course materials is crucial to the design and evaluation of pavement, which has a great effect on the life-cycle performance of pavement. In this study, the fatigue performance of commonly used stabilized base course materials was investigated. A general framework of degradation-based reliability was developed. To accurately characterize the degradation process of dynamic elastic modulus, a degradation index was proposed and its failure threshold values were defined. A degradation model to describe the evolution of degradation index was established and validated. A new approach to calculate reliability was established using Monte Carlo simulation. The corresponding degradation-based reliability was conducted on the fatigue test data. Results show that the value of critical degradation index is significantly influenced by the properties. The proposed degradation model is capable of predicting the degradation index with high degree of accuracy. The developed degradation-based reliability approach is able to capture the more real-degradation behavior of stabilized base course materials. The degradation-based reliability includes three phases, which correspond to different degree of cracking. The mean value of fatigue life corresponds to reliability decreasing phase.

Evaluation of cracking in asphalt pavement with stabilized base course based on statistical pattern recognition

Selection of optimal treatment strategy for a cracked asphalt pavement requires efficient evaluation of cracking. Pavement cracking severity was usually evaluated just by crack width in the past. In this paper, a novel method for extracting both crack type and crack width information in asphalt pavement with chemically stabilised base course from falling weight deflectometer (FWD) test data based on k-nearest neighbour (k-NN) pattern recognition was put forward. FWD field tests and core drilling tests were conducted at cracks on four typical expressways and a database with 215 deflection basins was established. Three feature sets were selected or extracted from each deflection basin as inputs. And, cracks were categorised into six classes based on crack type and crack width as target outputs. Results indicated that most cracks with high width level were thermal cracks and it was of great importance to consider both crack type and width in cracking evaluation in asphalt pavement with chemically stabilised base. Considering the classification accuracy and the convenience of test, crack was advised to be located between sensor S300 and sensor S600 in FWD field test. Deflection ratio feature set was recommended as inputs of the k-NN classifier.

연속철근 콘크리트궤도의 횡균열이 열차 하중에 의한 응력 분포에 미치는 영향

연속철근 콘크리트궤도에서는 온도 및 수분 변화에 따른 구속응력에 의해 횡균열이 발생한다. 이러한 균열은 연속철근 콘크리트궤도의 거동과 장기 공용성에 상당한 영향을 미치는 것으로 알려져 있다. 이와 같은 횡균열이 콘크리트궤도의 거동에 미치는 영향을 분석하고 균열 관리 기준을 보다 합리적으로 결정하기 위해, 이 연구에서는 연속철근 콘크리트궤도에 열차하중이 작용할 때 균열이 발생한 궤도 슬래브(TCL)와 기층(HSB)의 응력 분포를 3차원 유한요소해석 모델을 이용하여 예측하였다. 해석 결과에 따르면 균열 깊이가 증가할 경우 TCL의 휨응력과 TCL-HSB 경계부 수직응력이 증가하고, 균열이 슬래브를 관통할 경우 TCL 균열부에서 철근 주변에 국부적으로 수직 응력이 커져 장기적으로 펀치아웃 발생 가능성이 커질 수 있다. 반면 균열폭과 간격의 영향은 균열 깊이에 비해 크지 않은 것으로 나타났다. 따라서 균열폭과 간격만 관리하는 것보다는 균열 깊이를 동시에 관리할 필요가 있다. 또한 HSB 수축 줄눈의 위치를 침목 사이에 위치하도록 하는 것이 장기 공용성 확보에 더 유리하다. The restrained volume changes of concrete due to variations of temperature and moisture produce transverse cracks in continuously reinforced concrete tracks (CRCTs). Such cracks are known to significantly affect the behaviors and long-term performance of CRCT. To investigate the effects of the transverse cracks on the behavior of CRCT and to develop more reasonable maintenance standards for cracks, in this study, the stress distribution of the track concrete layers (TCL) and the hydraulically stabilized base course (HSB) with transverse cracks were numerically predicted by a three dimensional finite element analysis when CRCT was subjected to train loads. The results indicate that the bending stresses of TCL and vertical stresses at the interfaces between TCL and HSB increased as the cracks were deepened. In addition, vertical stresses were locally concentrated near reinforcing steel in cracks in TCL when full-depth cracks developed, which may lead to punch-outs in CRCTs. Comparably, the effects of crack width and spacing were not as significant as crack depth. This study indicates that ensuring the long-term performance of CRCTs requires adequate maintenance not only for crack width and spacing but also for crack depth. Our results also show that locating HSB joints between sleepers is beneficial to the long-term performance of CRCTs.

Beneficial Use of Coal Combustion By-products in the Rehabilitation of Failed Asphalt Pavements

� Abstract—This study demonstrates the use of Class F fly ash in combination with lime or lime kiln dust in the full depth reclamation (FDR) of asphalt pavements. FDR, in the context of this paper, is a process of pulverizing a predetermined amount of flexible pavement that is structurally deficient, blending it with chemical additives and water, and compacting it in place to construct a new stabilized base course. Test sections of two structurally deficient asphalt pavements were reclaimed using Class F fly ash in combination with lime and lime kiln dust. In addition, control sections were constructed using cement, cement and emulsion, lime kiln dust and emulsion, and mill and fill. The service performance and structural behavior of the FDR pavement test sections were monitored to determine how the fly ash sections compared to other more traditional pavement rehabilitation techniques. Service performance and structural behavior were determined with the use of sensors embedded in the road and Falling Weight Deflectometer (FWD) tests. Monitoring results of the FWD tests conducted up to 2 years after reclamation show that the cement, fly ash+LKD, and fly ash+lime sections exhibited two year resilient modulus values comparable to open graded cement stabilized aggregates (more than 750 ksi). The cement treatment resulted in a significant increase in resilient modulus within 3 weeks of construction and beyond this curing time, the stiffness increase was slow. On the other hand, the fly ash+LKD and fly ash+lime test sections indicated slower shorter-term increase in stiffness. The fly ash+LKD and fly ash+lime section average resilient modulus values at two years after construction were in excess of 800 ksi. Additional longer-term testing data will be available from ongoing pavement performance and environmental condition data collection at the two pavement sites.

Use of foamed asphalt in recycling incinerator ash for construction of stabilized base course

Use of incinerator ash in construction of highway pavement layers may have the potential to significantly reduce the quantity of ash that must be disposed of. However, the physical properties of ash are not optimal for construction of normal asphalt pavement. When designed and applied properly, foamed asphalt provides a way of obtaining good coating on granular materials made from ash and hence adequate cohesion of pavement materials. Also, foamed asphalt provides a way of using materials with relatively high percentage of fines and moisture content. This paper briefly reviews foamed asphalt and its use, production of aggregate from incinerator ash, and describes design, construction, and evaluation of a parking lot pavement using foamed asphalt-treated ash. Based on the results obtained from mix designs it was recommended that 2% lime be added to a mix with 100% ash (at optimum moisture content), and that 1% lime be used when 75% ash is combined with 25% recycled concrete-the recycled concrete being minus 12.5 mm material. For both 100% ash and the combination of 75% ash and 25% recycled concrete (minus 12.5 mm material) a design foamed asphalt content of 4.5% was recommended. Laydown and compaction of experimental foamed asphalt treated recycled ash mix was completed without any major problems. Results of Benkelman beam test showed that the foamed asphalt treated recycled ash mix layer cured and gained adequate stiffness within a period of 24 h.

Performance of Cold In-Place Recycling in Nevada

In light of the increasing cost of hot-mix asphalt (HMA) mixtures and the limited availability of good materials, cold in-place recycling (CIR) offers an attractive alternative for rehabilitating asphalt pavements. Because of its limited performance history and the unavailability of a standard mix-design procedure, the use of CIR mixtures has been limited to low-and medium-volume roads. For more than a decade, many highway agencies have experimented with or used CIR mixtures and reported numerous successes. The Nevada Department of Transportation (NDOT) is currently using CIR on low- and medium-volume roads. The CIR layer is treated as a stabilized base course followed by a thin HMA overlay. As part of this program, NDOT developed a mix-design procedure based on the Hveem mix-design method to establish the optimum moisture and emulsion contents. The design procedure evaluates the moisture sensitivity of the CIR mixture and determines the need for lime treatment of the CIR mix. The basic concept of the mix design is to assess the ability of the CIR process in providing a flexible and stable mix that can withstand the combined action of traffic loads and environment. The designed CIR mixtures were implemented on three field projects and showed excellent performance, which led NDOT to construct additional CIR projects.

Mechanical Stabilization of Cemented Soil–Fly Ash Mixtures with Recycled Plastic Strips

An experimental investigation was undertaken to evaluate the mechanical behavior of a soil–cement–fly ash composite, reinforced with recycled plastic strips (high-density polyethylene) that were obtained from postconsumer milk and water containers. The primary motivation for the study was to investigate the innovative reuse of several candidate waste materials in geotechnical and pavement applications. The specific objectives of the research were: (1) to evaluate the compressive, split tensile, and flexural strength characteristics of the material, and (2) to determine the effectiveness of recycled plastic strips in enhancing the toughness characteristics of the composite. Since cement-stabilized materials are weak in tension, the main focus of the experimental program was to conduct a series of specially instrumented split tensile and flexural tests on mixes containing various amounts of cement, fly ash, and plastic strips. For a meaningful comparison of test results, all specimens were prepared at a constant dry density. The standard ASTM C496 procedure for split tensile test was slightly modified by attaching two horizontal linear variable differential transformers (LVDTs) to measure the diametral deformation of the specimen due to compressive loading in an orthogonal direction. This modification enabled the evaluation of the postpeak toughness behavior of the composite. For some specimens, a strain gauge was attached to the middle of the face perpendicular to the loading plane in order to correlate the results with the one found using the LVDTs. All tests were performed with a 90 kN universal testing machine with deformation control. Experimental data show that the soil–cement matrix stabilized with 4% to 10% by weight of fly ash and reinforced with 0.25% to 0.5% (by weight) plastic strips (having lengths of 19 mm or 38 mm) can achieve a maximum compressive strength of 7000 kPa, a split tensile strength of 1000 kPa, and a flexural strength of 1200 kPa. These ranges in strength values are suitable for a high-quality stabilized base course for a highway pavement. To quantify the reinforcing effects in the postpeak region, a dimensionless toughness index is proposed. It is found that the use of fiber reinforcement significantly increases the postpeak load carrying capacity of the mix and thus the fracture energy. It is concluded that the lean cementitious mix containing recycled materials offer a lot of promise as an alternative material for civil engineering construction.

Use of Discrete Fibers for Tensile Reinforcement of an Alternative Pavement Foundation with Recycled Aggregate

Abstract An experimental investigation consisting primarily of splitting tension and flexural tests was conducted to perform a comparative evaluation of various fibers used to reinforce a stabilized base course material containing recycled crushed concrete aggregate, Type I portland cement and ASTM Class C fly ash. Three commercially available steel and polypropylene fibers, as well as high-density polyethylene (HDPE) fiber derived from recycled plastics were used in this study as reinforcing agents. The primary objective of using fibers was to improve the tensile strength, crack resistance, and toughness characteristics of this alternative pavement foundation material, which is composed of more than 90% by weight of waste products. As an extension to the ASTM C 496 procedure for splitting tension tests, two lateral linear variable differential transformers (LVDT) were attached at the mid-height of the specimens for measuring the tensile deformation of the horizontal diameter due to vertical compressive loading in the orthogonal direction. This method enabled the determination of splitting tension load-deformation and toughness behavior of the specimens. A dimensionless toughness index is used to quantify the post-peak behavior of the specimens containing various reinforcing fibers. A new dimensionless parameter, PPSI (Post Peak Strength Index), is introduced, which combines peak tensile strength with the energy absorption capacity of the composite for evaluating the effectiveness of fibers in a lean cementitious mix. It is found that depending on the mix proportions, the specimens reinforced with recycled HDPE strips can perform as well as or sometimes better than those reinforced with commercially available fibers. These observations are certainly encouraging from economical and environmental perspectives.

Investigation of Performance of Asphalt Pavement with Fly-Ash Stabilized Cold In-Place Recycled Base Course

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 capacity and structural number were also obtained from FWD test data. The structural coefficient of 0.16 was obtained for the fly ash–stabilized base course in the highway. The results of FWD testing indicate that CIR stabilization with self-cementing fly ash is an economical method of recycling flexible pavements and eliminates the need for expensive new granular base courses for road reconstruction.