Coarse Reclaimed Asphalt Pavement Research Articles

The Effect of Refined Separation on the Properties of Reclaimed Asphalt Pavement Materials

Refined separation not only controls the variability of reclaimed asphalt pavement (RAP), but also improves the mixing ratio of RAP and the quality of recycled asphalt mixtures. This study examines RAP treated with various refined separation frequency parameters, analyzes the variation rules and the variability of RAP aggregate gradation, asphalt content, asphalt properties, and aggregate properties, and calculates the maximum mixing percentage of coarse RAP material by using the gradation variability control method and the asphalt content variability control method. The results show that the variability of gradation and asphalt content of coarsely separated RAP is considerable, and a refined separation process significantly reduces the variability of gradation and asphalt content of RAP; the agglomeration of RAP decreases with an increase in the refined separation frequency; and the RAP agglomeration of three kinds of RAPs (E1, E2, and E3) under a refined separation frequency of 55 Hz reduces by 6.40%, 4.30%, and 4.30%, respectively, as compared with that of coarsely separated RAPs. The asphalt content of the refined separation RAP gradually decreases with an increase in frequency, and the asphalt content of E1 and E2 (55 Hz) was only 0.95% and 1.10%, respectively. The maximum percentage of RAP in recycled asphalt mixtures was calculated using the gradation variability control method and the asphalt content variability control method, respectively. The maximum proportions of RAP were 45% and 33% for A1 (0 Hz), respectively, and the maximum proportions of RAP for E1 (55 Hz) were all 100%. The results of the two methods show that the process of refined separation can increase the maximum proportion of blended RAP materials. They also demonstrate that the refined separation process can increase the maximum blending ratio of coarse RAP materials, thereby improving the quality of the RAP, increasing the proportion of RAP blending, and ensuring the quality of the recycled asphalt mixture. In conclusion, the refined separation process holds promise for maximizing the potential value of RAP and optimizing its recycling, environmental, and economic benefits.

Effect of RAP fractionation and dosage on design and mechanical behaviour of cold asphalt mixes

This study examines the effect of reclaimed asphalt pavement (RAP) material dosage and incorporation method on the mechanical characteristics of Cold Asphalt Mix (CAM). The RAP materials were fractionated into fine and coarse in addition to the unfractionated method. Four levels of RAP dosage (25, 50, 75, and 100%) were considered for each category. The mix design parameters, such as total fluid and emulsion content, were evaluated using the Indirect Tensile Strength (ITS) test. Overall, 455 specimens were prepared for mix design. The Optimum Emulsion Content (OEC) is the design emulsion content determined at peak value of ITS test. ITS, Indirect Tensile Stiffness Modulus (ITSM), and moisture susceptibility tests were conducted. Incorporating RAP in CAM increased the average tensile strength predominantly by 34% in coarse mixes, 28% in unfractionated, and < 10% in fine mixes. The average ITSM of the mixture increased by 30%, 60%, and 80% for fine, coarse, and unfractionated RAP. Further, emulsion demand was reduced by 53%, 43%, and 79% for fine, coarse, and unfractionated RAP, which showed that the RAP incorporation method profoundly influenced OEC. However, regardless of fractionation, CAM mixes showed lower cracking resistance and higher moisture susceptibility with increased RAP dosage. Two different conditioning protocols were used to capture the variation in moisture susceptibility for all 13 mix combinations. Coarse and unfractionated RAP mixes significantly differed in ITS, moisture susceptibility, cracking tolerance index, and ITSM. VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) approach was selected to rank the outperforming combination. The overall ranking of RAP incorporation showed that the coarse RAP mixes outperformed fine and unfractionated RAP mix characteristics. The study recommends restricting RAP usage by up to 75% to ensure the required performance of CAM mixtures.

Effect of Curing Temperature on the Shrinkage of Concrete Containing Reclaimed Asphalt Pavement: Experimental and Numerical Study

The aim of this research is to determine the effect of curing temperatures (20°C, 40°C, and 60°C) and incorporation rates of reclaimed asphalt pavement (RAP) on the mechanical properties and shrinkage of concrete made with reclaimed asphalt pavement (RAP-C). Five mixes were produced for this study: one with natural coarse aggregate and four with four replacement ratios of coarse RAP (25%, 50%, 75%, and 100%). The results show that the use of RAP reduces the workability and adversely affects the mechanical performance of RAP-C. Moreover, this study found that the total shrinkage increases with coarse RAP content. However, the total shrinkage of RAP-C decreases as the curing temperature increases: for concrete made with 100% RAP, a 20% reduction in total shrinkage was observed at 60°C compared to conventional concrete at 180 days. In addition, to predict the total shrinkage of RAP-C, finite element analysis using ANSYS© software based on the maturity approach and the two-phase serial model is used. The numerical results are in close agreement with the experimental data.

Quantifying the agglomeration effect of reclaimed asphalt pavement on performance of recycled hot mix asphalt

The utilization of reclaimed asphalt pavement (RAP) is becoming widespread in asphalt pavement industry. However, the agglomeration of RAP might exist during asphalt mixture production, which can affect the performance of asphalt mixtures. This study aimed to develop an innovative RAP agglomeration quantification method and investigate the agglomeration effect on performance of recycled hot mix asphalt (RHMA). The inherent agglomeration rate (IAR) and relative agglomeration rate (RAR) were defined and quantified by using the gradation curves. The RAP agglomeration was further determined under different mixing conditions including aggregate size, mixing time, temperature, etc. The influence of RAP agglomeration on hot mix asphalt mixture (HMA) was characterized through wheel rutting, low-temperature cracking, and moisture resistance testing. Results showed that RAP agglomeration do exist during asphalt mixture production, especially for high RAP content. The gradation curves from screening test proved to be an effective approach for RAP agglomeration quantification. The agglomeration rates of No.1, No.2, and No.3 RAP aggregates could be reduced by 5.7, 6.5 and 39.8 % under appropriate mixing conditions. But the fine RAP aggregates were easily re-agglomerated to form the coarse RAP aggregates. The ratio of 150 % between virgin coarse aggregate and RAP aggregate could avoid re-agglomeration issue for No.2 and No.3 RAP aggregates. Based on the rutting, low-temperature cracking, and moisture resistance tests, the impact of agglomeration phenomenon on the performance of plant RHMA with containing 100 % RAP was more than that with containing 50 % RAP.

Influence of key parameters on the performance of RAP-inclusive geopolymer concrete pavements: An approach integrating sensitivity analysis

The current study investigates the integration of Reclaimed Asphalt pavement (RAP) aggregates into geopolymer concrete, thereby providing a promising avenue for reinforcing sustainability in rigid pavement systems. Fly Ash (FA) and Ground Granulated Blast Furnace Slag (GGBS) based geopolymer mixes were designed to accentuate the performance with regards to varying molarity of NaOH (10 M-16 M), aggregate replacement levels (0%−100%) and curing periods. The experimental findings revealed a significant decrease in 28 days of compressive and flexural strength within 14 M-100% RAP mixes (57.6% and 39.7%, respectively). Nevertheless, GPC mixes incorporating 50% coarse RAP successfully met the prescribed strength criteria, making them suitable for Pavement Quality Concrete (PQC) applications. Additionally, the assessment of porosity and Water Absorption (WA) revealed a noticeable decrease with an increase in molarity as well as RAP fractions in the mix. Long-term performance was further assessed through resistance to surface abrasion, showing a maximum abrasive depth of 0.302 mm for 10 M-100%RAP mixes, thus affirming the durability of the RAP-GPC system. Rapid Chloride Penetration Test (RCPT) additionally demonstrated that the presence of adhered asphalt in RAP aggregates reduces porosity and enhances resistance to chloride ingress. Subsequently, the microstructural analysis and the study of solid-state NMR aided in comprehending the matrix behaviour, potentially linked to the performance of the mixes. The experimentally obtained compressive strength results were further statistically analysed through the Sensitivity Analysis (SA) approach, thereby providing a comprehensive understanding of the interplay between various strength-affecting parameters.

Influence of reclaimed asphalt pavement aggregate on the performance of metakaolin-based geopolymer concrete at ambient and elevated temperatures

Considering the environmental concerns surrounding conventional cement concrete production and the increasing demand for more sustainable and green materials, recent research considered utilization of recycled waste materials (e.g., aggregates from concrete construction and demolition, and reclaimed asphalt pavement) as full or partial substitutes for natural aggregates. Another direction of the research considered the production of more sustainable binders as an alternative to conventional cement (e.g., geopolymer or alkali-activated materials).To serve the objective of utilizing waste materials and reducing negative environmental impact associated with the use of cement concrete, the present study investigated the potential of producing metakaolin-based geopolymer concrete incorporating reclaimed asphalt pavement (RAP) aggregate. This research comprised experimental testing of five concrete mixes with 0%, 25%, 50% and 100% coarse RAP aggregate replacing the natural aggregate. Tests included compressive stress–strain behavior at ambient conditions (i.e., compressive strength, elastic modulus, strain at peak strength and toughness), and flexural strength. The performance after heat exposure to elevated temperatures of 300 °C and 600 °C was also tested. Proposed models for predicting the elastic modulus, strain at peak strength, flexural strength, and compressive stress–strain relationship matched the experimental results well. Results indicated that natural aggregate replacement by 25 % RAP aggregate caused a reduction in the compressive and flexural strengths by 42.8% and 26.2%, respectively. The increase in the RAP aggregate content enhanced the strain at peak strength e.g., the strain at peak strength was 42.9% higher than the control mix when 100% RAP aggregate was utilized.

Properties of pavement quality concrete prepared with coarse RAP containing different percentages of asphalt

ABSTRACT The present study was carried out to establish the proportion of Coarse Reclaimed Asphalt Pavement (C-RAP) containing varying percentages of asphalt for preparing Pavement Quality Concrete (PQC) mixes. RAP was collected from the 5-year-old pavement and separated into coarse RAP (C-RAP) and fine RAP (F-RAP) aggregates using a 4.75 mm sieve. Asphalt content in the C-RAP and F-RAP was found to be 4.12% and 4.33%, respectively. The C-RAP was immersed in the toluene solvent for a different predetermined time and asphalt content was reduced to 3.05%, 2.12%, and 1.24%. Using this exercise, C-RAP containing four different percentages of asphalt (4.12, 3.05, 2.12, and 1.24%) was produced. Then, the cement concrete mixes were prepared in the laboratory by replacing Natural Coarse Aggregate (NCA) with C-RAP varying from 25% to 100% with an increment of 25% in each type. Manufactured Sand (M-Sand)/Crushed Stone Sand (CSS) was used as a fine aggregate. Altogether, 17 concrete mixes (one control and 16 mixes containing C-RAP) were produced while keeping the water–cement ratio unchanged in all the mixes and evaluated their fresh and hardened concrete properties. As the asphalt presence in the RAP is sensitive to the temperature, the strength of concrete containing RAP at different temperatures was also examined. The current study showed that the amount of NCA substituted by C-RAP and the quantity of asphalt present in the C-RAP influenced the properties of concrete. The study also established that NCA up to 100% could be replaced with the C-RAP containing low asphalt content. Using test results, empirical models were developed to estimate the properties of hardened concrete by considering the percentage of C-RAP, percentage of asphalt in C-RAP, and compressive strength of concrete as predictor variables. The developed models were found statistically significant, supported by .

Refined decomposition: A new separation method for RAP materials and its effect on aggregate properties

In order to high-content and high-quality use of reclaimed asphalt pavement (RAP), the separation of aged asphalt and aggregates in RAP is necessary. However, the current separation methods are either inefficient, unsafe or costly. The objectives of this study are to propose a new separation method named refined decomposition (RD) and evaluate its separation efficiency and effect on aggregate properties. Quantitative indexes of asphalt removal percentage and weight loss percentage were proposed through asphalt extraction test to evaluate the separation degree of asphalt and agglomeration degree of RAP. The morphological and mechanical properties of RAP aggregates recycled from RD process were evaluated by aggregate imaging measurement system and crushing value test. The results showed that the separation degree is about 30–45 % and the agglomeration degree is reduced by 20 % for coarse RAP using RD method. The improved stability of the processed RAP is observed as well. The strength of aggregates is slightly enhanced, the angularity is slightly reduced, and the sphericity and texture are scarcely affected after RD process. In view of the acceptable changes in properties of aggregates, the RAP materials from the efficient RD process can be used in the pavement.

Aggregate packing characterisation of cold recycled mixtures

ABSTRACT Despite its significant role in cold recycling mix design and construction process, the effect of reclaimed asphalt pavement aggregates’ gradation and physical properties are relatively less understood. The ambiguities associated with the gradation effect led to challenges in determining the best practices in gradation control and stockpile management and blending in both cold-in-place and central plant recycling operations. Therefore, the main goal of this paper is to quantify the impact of gradation changes and proportioning of reclaimed asphalt pavement aggregates on the packing characteristics and performance of cold recycled mixtures. Binary blends consisting of fine and coarse reclaimed asphalt pavement stockpiles were combined to obtain fourteen gradations using a volumetric aggregate proportioning technique. The compatibility of five of the most prominent binary aggregate packing models was evaluated in cold recycling application. The modified Toufar model was able to accurately predict the blend of fine and coarse aggregates that offers the optimum packing prediction. Complex modulus tests showed linear viscoelastic characteristics of the cold recycled mixtures as well as the sensitivity to the packing states. In essence, this research shows the effectiveness of applying volumetric packing principles and aggregate proportioning techniques to achieve improvements in cold recycled mixtures’ volumetric and mechanical performance.

Effect of Aged Binder Distribution on the Fracture Tolerance of Asphalt Mixtures with Reclaimed Asphalt Pavement

Abstract This study investigated the effect of the distribution of aged binder from reclaimed asphalt pavement (RAP) on the fracture tolerance of recycled asphalt mixtures. Two RAP sources (one coarse, one fine), one virgin polymer-modified asphalt binder, and four RAP contents (0 %, 20 %, 30 %, and 40 %) were used to produce a total of seven mixtures. Fracture tolerance was assessed in terms of fracture energy density (FED) at three levels: binder, interstitial component (IC) (composed of effective binder and fine aggregate fraction), and mixture. Binder fracture energy tests were conducted to measure the FED of blends of virgin and recovered RAP binder. IC direct tension tests were employed to determine the IC FED. Finally, Superpave indirect tensile fracture tests were performed to obtain the FED of RAP mixtures. FED decreased with increasing RAP content at the three levels (binder, IC, and mixture). More importantly, IC and mixture exhibited almost identical FED reductions in relative terms, while the reduction was less significant at binder level. This finding indicates that the full blending scenario artificially created at the binder level did not occur at IC and mixture levels. Furthermore, the coarse RAP yielded greater FED than the fine RAP, which substantiates that RAP gradation controls the distribution of RAP binder in recycled mixtures. Consequently, the lower content of aged RAP binder in the IC portion for mixtures with the coarser RAP resulted in better fracture tolerance. The application of a newly developed guideline for determining the maximum allowable RAP content in recycled mixtures confirmed that the coarser RAP used in this study allows for a greater RAP content than the finer RAP despite the stiffer RAP binder.

Durability and Mechanical Properties of Roller Compacted Concrete Containing Coarse Reclaimed Asphalt Pavement

The feasibility of utilizing Reclaimed Asphalt Pavement (RAP) as a replacement for coarse aggregates in Roller Compacted Concretes (RCCs) was assessed. This replacement was performed in different volumetric percentages (25%, 50%, 75%, and 100%). During this process, RAP materials were subject to abrasion and impact in the Los Angeles drum and mixer before being added to the mixture. Compressive strength, splitting tensile strength, flexural strength, crack propagation, Ultrasonic Pulse Velocity (UPV), electrical resistivity, density, and water absorption (in 7, 28, and 90 days of age) tests were done on all mixtures. Results show that utilizing RAP in RCC can cause a drop in the mechanical properties, but it has positive effects on crack propagation of the specimens due to their increased toughness. Increasing the amount of RAP in the mixtures has increased their electrical resistivity, likely owing to the hydrophobic properties of RAP, which causes prevention from connecting pores to each other. The relationship between the mechanical properties and UPV of the mixtures was analysed using regression models. Moreover, one- and two-way ANOVA (analysis of variance) tests were performed on the results at a 95% confidence level. Finally, replacing the coarse aggregates with RAP only up to 75% is suggested if pre-processing is performed.

Utilization of cashew nut-shell ash as a cementitious material for the development of reclaimed asphalt pavement incorporated self compacting concrete

This paper focuses on developing sustainable self-compacting concrete (SCC) through the optimization process by incorporating Reclaimed Asphalt Pavement (RAP) as coarse and fine aggregates and also utilizing Cashew Nut-shell Ash (CNA) as a cementitious material. To achieve this optimization technique is implemented in four stages, which are the RAP aggregate treatment process, gradation selection process, RAP replacement percentage, and considering the CNA replacement percentage. RAP has been treated by a novel freeze–thaw cyclic procedure followed by the abrasion treatment method. Bailey's Aggregate Grading Technique (BAGT) has been implemented to line up the aggregate packing gradation. Mechanical and rheological properties have been conducted and analyzed based on compliance requirements of SCC at ambient temperature. Paste properties are analyzed through Field Emission Scanning Electron Microscopy, X-ray diffraction, Energy-Dispersive-Spectroscopy, and Thermo Gravimetric Analysis. Further, quality assessment of SCC has been performed through X-ray μCT (Xradia, XCT-500) and Ultrasonic Pulse velocity tests. In addition, compressive and flexural strength of selected SCC mixes have been performed at 50 °C, 100 °C, and 150 °C. Based on the results, with the incorporation of 75% coarse RAP, 50% fine RAP along 15% CNA as a binder constituent it becomes possible to achieve a sustainable SCC and it was found to be most suitable for real-time practices.

Laboratory investigation of Portland cement concrete paver blocks made with Reclaimed Asphalt Pavement aggregates

The present study investigates the potential of using Reclaimed Asphalt Pavement (RAP) aggregates for sustainable concrete paver blocks. Using RAP in its as-received state (with stiff asphalt coating, dust impurities, and agglomerated particles) and a higher proportion of coarse aggregates in the paver block mix design were some of the barriers tried to overcome during the experimental investigation. Fresh, mechanical and durability properties of five different mixes (including a control mix), volumetrically replacing the natural coarse aggregates with coarse RAP in the proportions of 25–100% (at an interval of 25%) were studied. Proper time-controlled compaction using a vibratory hammer and table vibrator helped adequately fabricating the paver blocks with a higher proportion of coarse aggregates in their aggregate skeleton. The results from this study indicated that the inclusion of RAP deteriorated the quality of the manufactured paver blocks both in terms of mechanical and durability properties. However, based on the performance, the paver blocks can be used for medium-traffic based applications.

Laboratory Investigation on the Fresh, Mechanical, and Durability Properties of Roller Compacted Concrete Pavement Containing Reclaimed Asphalt Pavement Aggregates

The present study evaluates the potential and suitability of different fractions of reclaimed asphalt pavement (RAP) for roller compacted concrete pavement (RCCP) mixes. Natural coarse and fine aggregates were replaced, partially and in combination, by coarse RAP, fine RAP, and combined RAP for preparation of RCCP mixes. The considered properties to determine the optimum RAP fraction and its proportion for RCCP were fresh density and water demand, compressive strength, flexural strength, split tensile strength, porosity, water absorption, abrasion resistance, and performance in aggressive environments of chloride- and sulfate-rich ions. It was observed that inclusions of all the fractions of RAP considered could reduce the strength related properties of RCCP mixes significantly at all curing ages. However, fine RAP mixes were found to exhibit better strength properties than coarse RAP and combined RAP mixes. It was also observed that none of the RAP mixes could achieve the recommended compressive strength criterion of 27.6 MPa, however, they exhibited enough flexural strength to replace a fraction of conventional aggregates, individually or in combination, for construction using RCCP. In fact, 50% coarse and 50% fine RAP mixes had higher flexural strength than the target laboratory mean strength of 4.3 MPa. Similarly, these mixes were found to have sufficient abrasion resistance and could be included in RCCP (surface course) to be constructed in areas having high concentrations of chloride and sulfate ions. Additionally, the results also indicated that higher proportions of fine RAP may be suggested for RCCP mixes to be laid in sulfatic environments.

Sustainable lean concrete mixes containing wastes originating from roads and industries

Abstract Scarcity of natural aggregates and illegal dumping of wastes originating from roads and industries are the major challenges for a developing country. The present study is an effort to provide a sustainable solution to the aforementioned challenges by utilizing these wastes for production of subbase course of concrete pavements. In the study, the optimum proportion of reclaimed asphalt pavement (RAP) along with the optimum proportion of the various supplementary cementitious admixtures (SCM) such as flyash (FA), silica fume (SF) and sugarcane bagasse ash (BA) have been evaluated for productions of dry lean concrete (DLC) mixes. The effect of the higher amount of Portland cement on the properties of RAP inclusive DLC mixes was also investigated. It was observed that the hardened properties of DLC containing RAP are mostly depended upon the maximum dry density of the fresh mixtures. Inclusions of considered industrial waste, as part replacement of Portland cement, were found to have an insignificant effect, whereas, when included in excess of cement, enhanced the properties of RAP-DLC blends significantly. The results of the study depicted that the suitability of RAP aggregates for DLC subbase may be increased by increasing the cement content by about 50%, whereas, for achieving the comparable performance to that of DLC containing natural aggregates, the quantity of cement shall be doubled. Based on the results of different parts of the study, it is recommended to include at least 30% extra cement content with either of 10% SF or 20% FA for sustainable DLC mixtures containing 75% coarse RAP aggregates.

Mix design formulation and evaluation of portland cement concrete paving mixtures containing reclaimed asphalt pavement

One potential solution to reduce the amounts of extra reclaimed asphalt pavement (RAP) stockpiles is to use RAP as an aggregate replacement in portland cement concrete (PCC).This study investigated whether partial replacement of virgin coarse aggregate by coarse RAP is a practically viable option to formulate PCC paving mixtures. The results showed thatreplacing virgin coarse aggregate by coarse RAP with sufficient intermediate size particles offers the benefits of achieving dense combined aggregate gradation. Measuring relevant mechanical properties followed by developing a procedure to determine optimum RAP replacement levels and guidelines and recommendations for designing PCC containing RAP were conducted and presented in this paper.

Characterisation of warm recycled porous asphalt mixtures prepared with different WMA additives

The use of Reclaimed Asphalt Pavement (RAP) into new asphalt mixtures and the reduction in the production temperatures by means of Warm Mix Asphalt (WMA) additives are two recognised solutions for sustainable pavements. Despite their environmental advantages, the reduced production temperatures of WMA mixtures may lead to rutting and moisture susceptibility issues. Such concerns need to be properly investigated, particularly in case of porous asphalt mixtures (PA) due to their low durability and high water sensitivity. The objective of this study is to evaluate the feasibility to reduce the production temperature of recycled PA including 15% of coarse RAP aggregates; three different WMA additives were selected (organic, chemical additive and zeolite) to produce PA mixtures at 130 °C. One HMA mixture was also prepared at 170 °C and an additional WMA mixture was prepared at reduced temperature without any WMA additive for comparison purposes. The experimental programme focused on compactability and durability properties of the PA mixtures. Results highlight the issues related to the reduced production temperatures of PA mixtures, particularly in terms of moisture susceptibility. Only the presence of the chemical additive in the mixture ensures adequate water resistance, although it does not guarantee short-term performance comparable to the HMA mixture.

Laboratory Investigation on Residual Strength of Reclaimed Asphalt Mixture for Cold Mix Recycling

The purpose of this study is to evaluate the residual strength of reclaimed asphalt pavement (RAP) to understand the strength forming mechanism of RAP in cold recycled asphalt mixture. The mechanical properties of the RAP were investigated as compared to the properties of pure aggregates. Triaxial shear tests were conducted to analyze the residual cohesion of asphalt binder in the RAP. The gradation and specific surface area of RAP were analyzed to understand the agglomeration structure of coarse RAP particles. Splitting strength of cement-RAP mixtures was tested as compared to cement-aggregate mixtures. It can be concluded that the RAP in the cold recycled asphalt mixture does not act exactly like ＂black color＂ aggregates. The aged asphalt in the RAP has active cohesion although its cohesion strength is much lower than the binder in the hot-mix asphalt mixture. The coarse RAP particles formed by agglomeration of fine particles and the aged binder have important influences on the strength of cold recycled asphalt mixtures. The cement-RAP mixture has much lower splitting strength than the cement-aggregate mixture with the same gradation and cement content. It is important to add new aggregate into the recycled mixture to increase the effective aggregate surface area that can be coated with the new binder.

Mechanical properties of roller compacted concrete containing rice husk ash with original and recycled asphalt pavement material

This study focused on the effects of rice husk ash (RHA) on the mechanical properties of roller compacted concrete (RCC) designed with original and reclaimed asphalt pavement (RAP) materials. The RCC mixes were produced by partial substitution of cement with RHA at varying amounts of 3% and 5%. Four aggregate combinations including the mix with original aggregate, coarse RAP+fine original aggregate, coarse original aggregate+fine RAP and total RAP were considered. The main experimental design consisted of the compressive strength and three points bending tests. Bending test was used to measure the modulus of rupture, material’s energy absorbency and analyse the fatigue response of RCC mixes. All tests were performed after 7, 28 and 120days curing except the fatigue test that performed on 120days specimens. Adding RHA resulted in higher optimum moisture content (OMC) and lower maximum dry density. Furthermore, adding RAP with different dimensions reduced the OMC and maximum dry density. The material’s flexibility improved upon replacing 3% cement by RHA. However, the energy absorbency reduced by increasing the RHA content to 5%. The fatigue life of RCC mixes containing RAP material was lower than the conventional one. Furthermore, replacing the coarse aggregate by RAP led to higher fatigue life than the fine aggregate. There was a strong relationship (R2>0.90) between the energy absorbency and fatigue response of RCC mixes. At higher stress ratios of 0.72, the mix with higher energy absorbency behaved better under repeated loadings. Besides, a reverse relationship was found between the fatigue life and material porosity. Adding 3% RHA reduced the porosity especially after 120days curing and improved the fatigue resistance. However, the addition of RHA to 5% resulted in higher porosities and lower fatigue lives.

Dynamic Modulus and Repeated Load Tests of Cold In-Place Recycling Mixtures Using Foamed Asphalt

As part of the validation effort to evaluate the consistency of a new cold in-place recycling using foamed asphalt (CIR — foam) mix design process for the Iowa Department of Transportation, the dynamic modulus and repeated load tests were conducted to evaluate the performance characteristics of CIR — foam mixtures over a wide range of loading and temperature conditions. The main objective of this research is to study the impacts of the foamed asphalt contents and reclaimed asphalt pavement (RAP) material characteristics on dynamic modulus and flow number. Dynamic modulus and repeated load tests were conducted on CIR — foam mixtures with RAP materials collected from seven different CIR project sites located throughout Iowa. Dynamic modulus values of the RAP materials varied depending on the sources and foamed asphalt contents. Coarse RAP materials with a small amount of residual asphalt content exhibited a higher modulus value at 4.4°C but exhibited a lower dynamic modulus value at 37.8°C than fine RAP materials with a large amount of residual asphalt content. Flow numbers were varied significantly depending on their RAP sources and foamed asphalt contents. Fine RAP materials with a hard residual asphalt binder exhibited a higher flow number than coarse RAP materials with a soft residual binder. The relative rankings of RAP materials in terms of the flow number did not change when the foamed asphalt was increased from 1.0 to 3.0%, which supports the repeated load test being consistent in evaluating a rutting potential of RAP materials.