Improving the Properties of RAP for Base Course Application by Blending RAP with A-3 Soil and Chemical Stabilization Using Asphalt Emulsion and Portland Cement PDF Download

Author: Rasha Riadh Salem AL-Obaydi
Publisher:
ISBN:
Category :
Languages : en
Pages : 248

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Book Description
The main objective of this research was to evaluate the effects of adding a combination of two stabilizing agents to blends of reclaimed asphalt pavement (RAP) with A-3 soil for use in a pavement base course. The California Bearing Ratio (CBR) and Marshall Stability tests were conducted on the blends to evaluate strength. Marshall flow and one-dimensional creep tests were performed to evaluate deformation. The test procedure in this study included one RAP/soil blend (75% RAP with 25% A-3 soil by weight) with five cement contents (0.0, 0.5, 1.0, 1.5, and 2.0% of type IIII Portland cement) and five asphalt emulsion contents (0.0, 0.5, 1.0, 1.5, and 2.0% of asphalt emulsion) added as chemical stabilizing agents. 100% pure RAP and 100% pure A-3 soil were also tested for CBR, Marshall Compression and Creep in order to set as a baseline to evaluate the improvement when the stabilizing agents were added.Results from this study showed that the unstabilized blends did improve in the strength compared to RAP or A-3 soil alone, but the blends did not meet the strength requirement for a base course material. Several combinations of chemical stabilizing agents increased the soaked CBR strength of the stabilized blends to between 76 and 78, but did not meet the standard of 80. Increasing cement content led to a linear increase in strength and reduced creep while increasing asphalt emulsion showed peak strength and creep reduction at between 1% and1.5% followed by a decrease in strength and increased creep at higher emulsion content. A strong linear positive correlation was found between the CBR and Marshall stability while a very weak positive correlation was observed between creep strain rate (CSR) and Marshall flow.

Author: Albert Marshall Bleakley
Publisher:
ISBN:
Category :
Languages : en
Pages : 668

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Book Description
Reclaimed Asphalt Pavement (RAP) is produced by milling during resurfacing operations. Finding innovative ways to incorporate RAP into highway base course applications will provide both environmental and economic benefits by allowing in situ recycling of material for projects such as widening or shoulder addition. RAP is a well-drained granular material which is already on site, however 100% RAP is low bearing strength and creeps under load. The objective of this research was to develop methods to improve RAP's strength while reducing creep to an acceptable level through blending with high quality crushed limestone aggregate and/or by chemical stabilization with asphalt emulsion, Portland cement, or lime. RAP/aggregate blends with and without chemical stabilization were compacted by modified Proctor, Marshall, or gyratory methods, cured, and tested for strength and creep. Strength tests included limerock bearing ratio (LBR), a variant of the CBR test, unconfined compression, Marshall compression, and indirect tensile tests. Strength specimens were tested dry and soaked to evaluate retained strength. One dimensional creep testing was performed using seven day oedometer tests. RAP/aggregate blends have the potential to be used successfully as a base course material. Blends of RAP with 50% limerock base material attained a soaked LBR strength of 100 and acceptable levels of creep with the addition of 1% of either asphalt emulsion or cement. Blends of RAP with 75% or more limerock attained a soaked LBR close to 100 and low levels of creep without any chemical stabilizer. In general adding RAP to limerock blends increased the soaked retained strength and improved permeability compared to 100% limerock. Gyratory compaction achieved higher densities than modified Proctor or Marshall compaction and improved RAP's strength by a factor of two to three compared to modified Proctor compaction at the same density but had less effect on creep. Field testing is required to determine whether it is feasible to reproduce the gyratory compaction results on an actual construction site. Significant variability was noted between results with different blends, compaction methods, and stabilizing agents. Site specific performance testing should be conducted to establish the viability of blending RAP into a base or subbase.

Author:
Publisher:
ISBN:
Category : Pavements, Asphalt
Languages : en
Pages : 561

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Book Description
The objective of this study was to improve Reclaimed Asphalt Pavement (RAP) strength in base course applications while reducing creep to an acceptable level using compaction techniques, fractionating, blending with high quality base course aggregate, and/or by chemical stabilization with asphalt emulsion, Portland cement, or lime. RAP/limerock blends with and without chemical stabilization were compacted by modified Proctor, Marshall, or gyratory methods, cured, and tested for strength and creep. Strength tests included limerock bearing ratio (LBR), unconfined compression, Marshall compression, and indirect tensile tests. Strength specimens were tested dry and soaked to evaluate retained strength. Seven-day one-dimensional creep testing was performed. Gyratory compaction produced higher densities than modified Proctor or Marshall compaction. At the same density, gyratory compaction improved RAP strength by a factor of two to three over modified Proctor but had less effect on creep. Modified Proctor moisture-density plots followed an S-shape without a clear optimum; modified Proctor may not be the best method to predict RAP compaction behavior. Fractionating RAP did not improve strength or creep unless RAP was remixed to match a maximum density curve. Fractionating did not produce acceptable LBRs or creep. RAP blended with limerock, cemented coquina, or reclaimed concrete aggregates showed improved LBR and creep performance. RAP/aggregate blends have the potential to be used as Florida base course. As the amount of aggregate blended with RAP increased, LBR increased and creep decreased. Creep behavior of blends with 75 percent aggregate was similar to 100 percent aggregate. Unstabilized blends with 50 percent aggregate did not produce LBR values over 100. Blends of 50 percent RAP/50 percent limerock stabilized with 1 percent of either asphalt emulsion or cement attained soaked LBRs over 100 and acceptable creep. Blends of RAP with 75 percent limerock attained soaked LBRs close to 100 and low creep without any chemical stabilizer. Adding RAP to limerock blends generally increased the soaked retained strength and improved permeability compared to 100 percent limerock.

Author: Blnd Jasim Othman
Publisher:
ISBN:
Category :
Languages : en
Pages : 278

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Full depth reclamation (FDR) is apavement repair method that uses in-place milling and recycling of existing asphalt to rehabilitate roads. The FDR process includes milling the existing pavement, blending the crushed pavement with underlying aggregate materials and chemical stabilizing agents to create a new stabilized base course. Usually a thin wearing course in placed on top of the stabilized base. The purpose of this research was to investigate the effects of a combination stabilizing agents added to different blends of reclaimed asphalt pavement (RAP) and high quality limerock aggregate base material on the strength and creep of blended materials. Strength and deformation of the blends were evaluated using the California Bearing Ratio (CBR), modified Marshall, and one-dimensional oedometer creep tests. Blends of RAP and limerock base were blended with Portland cements and asphalt emulsion in varying proportions. Blends in this study were prepared at 0%, 25%, 50%, 75%, and 100% RAP by weight. Specimen mixtures consisted of25, 50, and 75 percent RAP stabilized with 0.0, 0.5, 1.0, 1.5, and 2.0 percent Type I/Il Portland cement and 0,0, 0.5, .1.0, 1.5, and 2.0 percent Cationic Asphalt Emulsion (CSS-1H) by weight. The 0% RAP samples were controls of pure limerock aggregate; 100% RAP samples were controls of pure RAP. The objective of these projects was to obtain baseline data and to evaluate stabilizing, curing and testing techniques for chemically stabilized specimens. Increasing RAP content decreased the strength and increased the deflection of blends. For blends without chemical stabilization, only the 25% RAP/75% Iimerock blend achieved an average soaked CBR over 80. For chemically stabilized blends, increasing cement content always increased strength and decreased deflection. Asphalt emulsion stabilized blends showed peak strength (CBR and Marshall Stability) at 1% and 1.5% emulsion for 50% and 25% RAP blends. A very good correlation was found between soaked CBR and soaked Marshall stability with an average R2 of 0.73.

Author: Dallas N. Little
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 264

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Author: Asphalt Institute
Publisher:
ISBN: 9781934154175
Category : Asphalt
Languages : en
Pages : 102

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Author: Hawraa Kadhim
Publisher:
ISBN:
Category : Asphalt concrete
Languages : en
Pages : 158

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Book Description
Reclaimed Asphalt Pavement (RAP) has been favoured over virgin materials in the light of the unstable cost of virgin asphalt binders, shortage of quality aggregates, and compelling need to preserve the environment and natural resources. Mixes containing up to 20% RAP are commonly considered to have similar behaviour to virgin mixes. However, during the production process of HMA with RAP, the blending between aged and virgin binders would be partial, which would create heterogeneity in distribution of the aged recycled binder and the soft virgin binder in the HMA-RAP mixes. Hence, it is important to control the blending process between old and new binders to obtain more homogenous mix. Therefore, the main objectives of this research are to examine the kinematics of blending of aged and virgin binders by considering the time-temperature effect during mixing and silo-storage, and assess the thermo-mechanical behaviour of Hot Mix Asphalt (HMA) containing RAP at different blending states. The asphalt mixes used in this research were produced and collected at two plants (Plant 1) and (Plant 2) located in Ontario, Canada. Two Marshall mixes were produced and collected from Plant 1 including a surface course HL-3 containing 15 percent RAP and a base course HL-8 containing 30 percent RAP. These mixes were labelled as 1HL-3 and 1HL-8 respectively. In addition, two Marshall mixes were produced and collected from Plant 2 including a surface course HL-3 containing 20 percent RAP and a base course HL-8 containing 40 percent RAP. These mixes were labelled as 2HL-3 and 2HL-8 respectively. To investigate the impact of storage time on the blending progress and achieving a cohesive final binder, the mix samples were collected as a function of storage time in the silo. The first sampling was done immediately after production (t = 0-hour), and then at several time intervals of silo-storage; i.e., at 1, 4, 8, and 12 hours. In case of Plant 2, the samples were additionally collected after 24-hour of storage time. All samples were then kept in a storage room at 7ʻC until the day of compaction to minimize any further blending between aged and virgin binder. To understand the blending phenomena and its effect on the performance of the pavement, a multi-scale investigation is carried out. The blending was examined in terms of micro-mechanical and rheological properties. The microstructure of the blending zones were examined under The Environmental Scanning Electron Microscope (ESEM). In addition the effect of the silo-storage time on the rheology of the binders was investigated. The results indicate that increasing the interaction time and temperature between the aged and virgin binder significantly results in a better blending. The performance of RAP-HMA with respect to the silo-storage time was examined using Dynamic Modules Test, Thermal Stress Restrained Specimen Test (TSRST), Rutting Test, and Flexural Beam Fatigue Test. The experimental data indicates that samples collected after 12-hour of silo storage exhibited a reduction in the stiffness due to better blending of aged and virgin binder. In addition, the 12-hour samples showed enhancement in their fracture temperature, rutting depth, and fatigue life, accompanied with a better blending between their aged and virgin binder. On the other hand, the samples that collected after 24-hour silo-storage had a higher stiffness in comparison with the 8 and 12-hour samples. Moreover, the AASHTOWare Pavement Mechanistic-Empirical Design was utilized to examine the effect of the 12-hour silo-storage time on the long term performance of the pavements. Four pavement structures have been designed for this purpose. These pavements have the same structure of their granular A, granular B, and the subgrade. Yet, the first layer (surface course and base course) is a silo-storage time-dependent. The long-term field performance prediction indicates a slight improvement with the 12-hour pavements (Plant1 12hrs and Plant2 12hrs). However, it should be noted that AASHTOWare Pavement Mechanistic-Empirical Design does not appear to properly capture the effect of blending in the pavement performance. The collected experimental evidences unveils correlations between time-temperature effects and mixture performance. Based on these findings, the research provides practical recommendations to the professionals of the Canadian asphalt industry for a better use of RAP. Ultimately, this research recommends a 12-hour silo-storage time for the RAP-HMA for better performance and durability of the mixes.

Author: Soheil Nazarian
Publisher:
ISBN:
Category : Asphalt concrete
Languages : en
Pages : 12

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Book Description
Reclaimed asphalt pavement (RAP) and granular base materials were collected throughout Texas to evaluate the properties of RAP and RAP blended with virgin or salvage aggregates for roadway base course application. Mixes containing RAP of 100 %, 75 %, and 50 % and treated with Portland cement of different dosages were utilized in a comprehensive laboratory testing program. The factors that affect the properties of cement-treated RAP mixes are identified and a mix design model based on typical RAP and granular base materials in Texas was proposed. The design model was verified by the data from the initial field trial on actual construction projects. The feasibility of using a modulus-based procedure for quality assurance/quality control during construction is discussed.

Author: Deren Yuan
Publisher:
ISBN:
Category : Cement
Languages : en
Pages : 86

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Book Description
Reclaimed asphalt pavement (RAP) and granular base materials were collected from stockpiles in six TxDOT districts to evaluate the feasibility of using high RAP content mixes for base course applications. Mixes containing 100%, 75% and 50% RAP treated with Portland cement of 0%, 2%, 4% and 6% were evaluated in a full-factorial laboratory experiment. For mixes of 75% and 50% RAP, both virgin and salvage base materials, when available, were used.

Author: Rita M. Issa
Publisher:
ISBN:
Category : Pavements, Asphalt
Languages : en
Pages : 90

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Book Description
A field demonstration project was undertaken by the Oklahoma Department of Transportation to investigate the performance of an asphalt overlay constructed using recycled asphalt millings and the cold mixed, cold laid system. A 1.9-km (1.2-mi) section of the US-64 North frontage road in Pawnee County was rehabilitated with a 5-cm (2-in.) thick overlay using 100% recycled asphalt millings. The section was divided into four approximately equal length test sections. A different type of emulsion was used to rejuvenate the asphalt millings for each test section. The purpose was to determine the relative performance of each emulsion type and construction method used in this recycled asphalt pavement (RAP) project. A laboratory investigation was carried out to accomplish two major tasks: the first task was to determine the optimum emulsion and moisture contents of RAP mixes prepared with four different types of emulsions; the second task was to investigate the effect of adding portland cement to RAP mixes, thus producing a cement-emulsion composite.