RAP Aggregates Research Articles

Study on the correlation between homogeneity of mastic and aggregate skeleton on cracking resistance of recycled asphalt mixtures

ABSTRACT The heterogeneous distribution of mastics and aggregates affects the durability of recycled asphalt pavements through cracking and failure behaviour. This study used force chain network analysis to quantify the homogeneity index of stress transfer and established correlations between this homogeneity and the cracking resistance of recycled asphalt mixtures. The results showed a good correlation of 0.8288 between the horizontal homogeneity index DH2, based on the area ratio of RAP and virgin aggregates, and fracture energy Gf. Additionally, the stress transfer efficiency index DH had a significant correlation of 0.7975 with Gf. Bending Beam Rheological tests revealed a high correlation of 0.9507 between the low-temperature performance index S/m and Gf, and a moderate correlation of 0.6115 between the homogeneity index Dm of blended mastics and the coefficient of variation of Gf. Thus, this study established a model that correlated the homogeneity of blended mastic and mixtures with the crack resistance of recycled asphalt mixtures, achieving a correlation coefficient of 0.8492 between the predicted and actual results. These findings enhance the understanding of the relationship between mixture homogeneity and mechanical properties, advancing virtual design technologies for recycled asphalt mixture design.

Laboratory investigation of concrete paver blocks containing RAP aggregates, fly ash and GGBS

Laboratory investigation of concrete paver blocks containing RAP aggregates, fly ash and GGBS

Performance of Alkali-Activated Fly Ash Stabilized High Percentage RAP Aggregates as a Pavement Base Course: Laboratory and Field Perspectives

Performance of Alkali-Activated Fly Ash Stabilized High Percentage RAP Aggregates as a Pavement Base Course: Laboratory and Field Perspectives

A detailed laboratory investigation on evolving the mix design of roller compacted concrete containing RAP aggregates and SCMs

A detailed laboratory investigation on evolving the mix design of roller compacted concrete containing RAP aggregates and SCMs

Influence of different curing conditions on the transport, durability and microstructural properties of concrete paver block mixes containing RAP aggregates

Influence of different curing conditions on the transport, durability and microstructural properties of concrete paver block mixes containing RAP aggregates

Development of Pervious Paver Block Using Sugarcane Bagasse Ash & RAP Aggregates

Abstract: This particular kind of concrete is distinguished by its interconnected pore structure and significant void content or porosity, which typically varies from 15 to 35% by volume. Pervious concrete may lower the danger of flooding, diminish stormwater runoff, reduce noise when in contact with automobile tires, and avoid glare and skidding during rainy seasons by allowing water to easily infiltrate through its pores and replenish the ground water table. Considering the condition of the neighboring roadways, a modest effort is undertaken to construct the least amount of porous paver concrete. For the planned Mix proportions, compression strength, void ratio, and infiltration tests were conducted. In the current study, 60mm thick pervious paver blocks for medium traffic with different RAP aggregate percentages and sugarcane bag ash are cast. This improves the compressive strength. RAP aggregates are a suitable material that may be utilized in place of natural and artificial aggregates in construction projects. The thesis shows how discarded sugarcane ash may be used again. Several experiments were conducted to evaluate the compressive strength, density test, porosity, and permeability of the planned paver block as well as its durability.

Stabilization of cement-treated base mixes incorporating high reclaimed asphalt pavement materials using stabilizer rich in SiO2 and Al2O3

Using RAP material can be one of the promising solutions for solving the new material issues, reducing haulage distance and fuel cost to a great extent as the complete process is done at site only using the Full-depth reclamation (FDR) technique. However, the effect of the high amount of RAP material with stabilizer has not been completely understood for constructing the CTB layer. In the present study, a mixed design of the CTB layer has been formulated considering the requirements of Indian Specifications to utilize maximum RAP material in a sustainable approach. Mechanical and durability properties of CTB mix were evaluated to identify the effect of different cement, stabilizers, and RAP aggregates on the laboratory mixtures. The efficacy of stabilizer with cement was examined to judge the suitability of the same as potential pavement construction materials. The optimal mix was decided mainly based on the Unconfined Compressive Strength (UCS) value and flexural strength of aggregate specimen at 7-days of moist curing. However, for a detailed study, UCS values were checked at three days, seven days, and 28 days. Also, the durability properties of the CTB mix were analyzed by performing a durability test, sorptivity, and rapid chloride penetration test (RCPT). Present laboratory studies firmly indicated that using a stabilizer with cement using 70 % RAP leads to a strong and durable CTB mix.

Evaluating reclaimed asphalt mixture homogeneity using force chain transferring stress efficiency

Numerous studies have demonstrated a direct link between the homogeneity of asphalt mixture and the rutting performance, water stability, tensile strength, and service life of the asphalt pavement. Due to the existence of RAP clusters, poor homogeneity of the recycled asphalt mixtures is more severe than natural ones. However, previous studies have mainly focused on analyzing the distribution of aggregates, ignoring the transfer of the internal stress in the mixture. This paper proposed a novel approach for the analysis of the homogeneity of recycled asphalt mixture using the efficiency of force chain transferring stress. Therefore, to prepare gyratory compacted samples, diabase in green color was used as the virgin aggregate and marble in white color as the RAP aggregate. Moreover, to obtain the vertical section images, the samples were cut and processed by digital image processing (DIP). This included distinguishing the virgin and RAP aggregates by global gray threshold segmentation, adding asphalt film around the aggregates, and constructing a force chain network relied on the aggregate contact information. Also, the intensity of the force chain was determined using the finite element method (FEM). In addition, the efficiency of force chain transferring vertical stress (ETVS) was introduced and the homogeneity index D of the recycled asphalt mixture was proposed based on the variation coefficient of ETVS. Furthermore, uniaxial compression tests were carried out to mathematically analyze the homogeneity index D proposed in this paper and the homogeneity index D′ proposed based on the aggregate area ratio in previous studies. The obtained result showed that the homogeneity index D increased first and then decreased with the increase of RAP content. Moreover, the correlation analysis demonstrated the compressive performance of the mixture to be mainly reflected by the homogeneity index D. The correlation coefficients of the compressive strength and the compressive resilient modulus were found to be 0.9010 and 0.8464, respectively. Finally, the homogeneity index D′ was observed to mainly reflect the stability of the compressive performance of the mixture, with the correlation coefficients of the variation coefficient of the compressive strength and the compressive resilient modulus of 0.8745 and 0.8869, respectively.

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 .

Evaluating the effects of using reclaimed asphalt pavement and recycled concrete aggregate on the behavior of hot mix asphalts

In this research, the performance of hot mix asphalts mixes (HMA) with RAP and RCA was evaluated, in terms of their Marshall stability, flow, and volumetric properties, to verify their applicability as a replacement for the natural aggregate in the flexible pavement surface layers of HMA mixtures. The experimental work was divided into two phases; the first phase investigated the crushed limestone, white hard-rock, and basalt aggregate materials with a nominal maximum aggregate size of 19 mm. The second phase studied the replacement of crushed limestone, by weight, with the RAP and RCA at different asphalt cement contents. The coarse and fine aggregate of the recycled materials were used at four percentages of 25%, 50%, 75%, and 100%, respectively. The experimental test results showed that replacing limestone with recycled aggregate materials affected the mechanical characteristics, mainly the volumetric properties of the HMA. Using RCA in the hot asphalt mixes violated the upper limit of 5% for the air voids property and increased the optimum asphalt content (OAC) up to 5.96% for mixes prepared with 50% RCA. The results also revealed that adding RAP aggregate to the limestone in the HMA improved their Marshall stability, and the highest value of 29.32 kN was recorded for the asphalt mixes prepared with 75% RAP at 3% asphalt content. The combination of RAP and RCA aggregates indicated that as the RCA proportion in the mix increased, lower load capacity was observed and higher OAC compared to the other asphalt mixes.

Hydrological and Strength Characteristics of Pervious Concrete Mixes Containing RAP Aggregates and Sugarcane Bagasse Ash

Abstract Pervious concrete (PC) is a new type of concrete that is gaining popularity because of its low-impact development capabilities and ability to reduce stormwater runoff. The current study focuses on the potential use of waste from the sugarcane industry and on flexible pavement, specifically sugarcane bagasse ash (SBGA) and reclaimed asphalt pavement (RAP), to create PC mixes. Furthermore, an unconventional method was used to extract the benefits of RAP without compromising the structural integrity of PC: designing the mixture based on hydrological properties rather than mechanical parameters and then improving structural integrity through the use of SBGA without compromising the hydrological capacity of the designed PC mixture. Six PC mix combinations were developed by substituting recycled asphalt pavement for natural coarse aggregate in varying proportions of 0, 50, and 100 %. Following that, three RAP-incorporated PC mixes were created using 5, 10, and 15 % SBGA as a partial replacement for cement. It was discovered that using SBGA as a partial replacement for cement reduces mechanical properties while increasing functional properties such as permeability. Surprisingly, no significant differences were observed in the percentage voids of PC mixes containing RAP aggregates. The addition of 10 % SBGA significantly improves the mechanical properties of 100 % coarse RAP (cRAP)-inclusive PC mixes. When the total cost of 1 m3 concrete was calculated, the addition of cRAP aggregates and SBGA in pervious concrete pavements mixes resulted in a 44 % reduction. Furthermore, the current study suggests replacing 10 % of ordinary Portland cement with SBGA in cRAP inclusive PC mixes, as this increases the strength of cRAP–PC mixes while also providing environmental and economic benefits.

The study of the feasibility of using recycled steel slag aggregate in hot mix asphalt

Significant growth in the road network around the world has increased the need for pavement materials. The growing demand for producing original asphalt pavements from non-renewable natural resources can deplete natural resources, cause environmental issues, and consume significant amounts of energy. The idea of using waste materials such as steel slag or reusing recycled aggregated of old pavements was evaluated to increase the sustainability of pavements. Rutting resistance, marshall stability, moisture susceptibility, resilient modulus, and fatigue life of slag and conventional asphalt mixtures containing different percentages (0, 25, 50, and 75 wt%) of (Recycled Asphalt Pavement) RAP or slag aggregates were compared to evaluate the mechanical performance of recycled asphalt with slag aggregate, The recycled asphalt mixtures were rejuvenated by 3 or 6 wt% of automobile waste oil. The results showed that slag asphalt had a better performance in all areas. Additionally, replacing the original aggregate with RAP or recycled slag improved marshall stability, tensile strength, and rutting resistance of the asphalt or slag asphalt mixture. Using higher percentages of the recycled aggregate resulted in further improvements. The fatigue life of the recycled samples increased under loading with low strain level when higher percentages of the recycled aggregate were replaced, but it reversed at higher strains. Finally, the results indicated that using recycled steel slag for producing hot mix asphalt could produce a more durable asphalt in comparison to using RAP.

Preliminary Study on New Alternative Binders through Re-Refined Engine Oil Bottoms (REOBs) and Industrial By-Product Additives.

Recent studies have worked towards addressing environmental issues such as global warming and greenhouse gas emissions due to the increasing awareness of the depletion of natural resources. The asphalt industry is seeking to implement measures to reduce its carbon footprint and to promote sustainable operations. The reuse of several wastes and by-products is an example of a more eco-friendly activity that fulfils the circular economy principle. Among all possible solutions, the road pavement sector encourages, on one hand, the use of recycled materials as a partial replacement of the virgin lithic skeleton; on the other hand, it promotes the use of recycled materials to substituting for a portion of the petroleum bituminous binder. This study aims to use Re-refined Engine Oil Bottoms (REOBs) as a main substitute and additives from various industrial by-products as a full replacement for virgin bitumen, producing high-performing alternative binders. The REOBs have been improved by utilizing additives in an attempt to improve their specific properties and thus to bridge the gap between REOBs and traditional bituminous binders. An even larger amount of virgin and non-renewable resources can be saved using these new potential alternative binders together with the RAP aggregates. Thus, the reduction in the use of virgin materials is applied at the binder and the asphalt mixture levels. Rheological, spectroscopic, thermogravimetric, and mechanical analysis were used to characterize the properties, composition, and characteristics of the REOBs, REOB-modified binders, and asphalt mixes. Thanks to the rheological investigations of possible alternative binders, 18 blends were selected, since they behaved like an SBS-modified bitumen, and then they were used for producing the corresponding asphalt mixtures. The preliminary mechanical analysis of the asphalt mixtures shows that six mixes have promising responses in terms of stiffness, tensile resistance, and water susceptibility. Nevertheless, the high variability of recycled materials and by-products has to be taken into consideration during the definition of alternative binders and recycled asphalt mixtures. In fact, this study highlights the crucial effects of the chemical composition of the constituents and their compatibility on the behaviour of the final product. This preliminary study represents a first attempt to define alternative binders, which can be used in combination with recycled aggregates for producing more sustainable road materials. However, further analysis is necessary in order to assess the durability and the ageing tendency of the materials.

Microstructural Mechanical Analysis of Warm‐Mixed Reclaimed Semiflexible Pavement Materials with Interfacial Weakening Effect

Warm‐mixed reclaimed asphalt pavement technology, as an environmental recycling method to reuse waste materials, has been widely investigated around the world. However, the skeleton of the reclaimed asphalt mixture is unstable due to the existence of the reclaimed materials. Semiflexible pavement has been successfully used in heavy traffic area due to its high rutting resistance. For combination with these two methods, a warm‐mixed reclaimed semiflexible pavement material was proposed in this study. In order to investigate the interfacial weakening effect of the warm‐mixed reclaimed semiflexible pavement material in a microstructural perspective, an image‐based two‐dimensional microstructural finite element model was presented. Results show that the maximum compressive stress of the new and RAP aggregates and cement mortar with interface is greater than that without interface and the compressive stress of the material increases when considering the interface. Besides, the maximum compressive strain of the material with interface is greater than that without interface and the strain values in the models with interface at all three positions are greater than those without interface.

Permanent deformation analysis of base layers with recycled material: Effect of density and stress level

Full-depth reclamation techniques present numerous advantages for pavement rehabilitation strategies. The recycling process produces a thick layer of stabilized or unstabilized reclaimed materials, which is used as a new base layer of RAP aggregates. The compaction of the unstabilized thick layer is critical for adequate permanent deformation behaviour of the reclaimed layer. In some agencies, the smooth drum compaction is often used directly after the recycling process to compact the reclaimed materials. Previous studies demonstrated the challenges associated with adequate densification of the thick reclaimed layer through its whole thickness, leaving among other a material with a vertical density gradient. In that context, this study was designed to quantify the effect of the degree of compaction on the permanent deformation behaviour using cyclic triaxial tests. Granite and limestone aggregates were mixed with RAP in order to obtain mixes with 50% RAP, and each blend was tested using a permanent deformation test procedure at four different degree of compaction. One of the tested degree of compaction was a varying compacted density over the sample height. It was found that the analysis of this particular sample performance could be done on the basis of the average dry density of the sample. The shakedown ranges of each sample were analyzed with respect to stress ratio and degree of compaction. The behaviour for each type of mix was also similar. A generalized model was therefore proposed allowing to predict the range of permanent deformation behaviour knowing stress level and the degree of compaction. The general model between shakedown range and a relative stress ratio is based on a shift factor linking the effect of stress and density. Limit states were also defined for the possible ranges of behaviour with respect to the degree of compaction.

Zinc Waste as a Substitute for Portland Cement in Roller-Compacted Concrete Pavement Mixes Containing RAP Aggregates

AbstractOwing to heavy toxic metal concentration such as copper, lead, zinc, sulfur, cadmium, and chromium, jarosite particles from the zinc industry are considered a hazardous waste material. Prop...

Characterization of Classified Indian Reclaimed Asphalt Pavement RAP Aggregate Impact Value and Aggregate Abrasion Value of Rap Aggregates

Reuse of existing deteriorated bituminous pavement material in construction and maintenance of flexible pavement is called recycling of bituminous pavement. Removed and reprocessed deteriorated pavement material which is recycled is termed as Reclaimed asphalt pavement (RAP). In India during construction of flexible pavement different types of bituminous layers are in practice depending upon CBR of sub-grade and traffic count i.e. CVPD of the road stretch. Depending upon types of bituminous layer i.e. PC Seal Coat, Bituminous Macadam(BM), Dense grade bituminous Macadam (DBM), Semi Dense Bituminous Concrete (SDBC) or Bituminous Concrete(BC) Reclaimed Asphalt Pavement can classified in different groups These classified RAP groups materials will have different characteristics i.e. Rap aggregates and Recovered bitumen of different group of RAP will have different characteristics. In this study characterization of RAP limited to Aggregate Impact Value (AIV) and Aggregate Abrasion Value (AAV)of RAP aggregates of RAP classified in different groups. Results of this study will be compared to standard value of AIV and AAV required for bituminous construction to predict that RAP aggregates are suitable or not for use in bituminous mixes.

Effect of Utalization of Natural Aggregates by Rap Aggregates and Cement by Ggbs in Alkali Activated Concrete Pavement

Coarse aggregates and cement are the main constituents of the concrete in the rigid pavement structure. The procurement and generation of natural aggregates are getting difficult day by day because of a lack of natural resources. Search for alternatives to natural coarse and fine aggregates leads to the usage of Reclaimed Asphalt Pavement aggregates, which are produced abundantly due to the replacement of flexible pavement with the rigid pavement. Ground Granulated Blast Furnace Slag (GGBS) is a waste material/by-product from steel and iron industries that can be used as an alternative binder in the alkali enacted system in place of cement. This study is taken up to determine the physical properties of materials, strength parameters and durability aspects of alkali-activated concrete are studied with GGBS which is the complete replacement for cement. The RAP aggregates are procured from KR market flyover Bangalore. And it is checked in the effective utilization in geopolymer concrete pavements. RAP fine aggregates and RAP coarse aggregates are partially replaced with river sand and natural aggregates with a variation of 100%, 75%, 50%, and 25% for M40 grade of concrete. Na2O dosage of 4.5% and activator modulus of 1.25 is taken and kept constant throughout the study. The cubes, cylinders and beams were casted and tested for strength. And fatigue test and non destructive test such as ultrasonic pulse velocity and rebound hammer test is conducted. The results can be analyzed to identify the importance of RAP fine aggregates and RAP coarse aggregates in the geopolymer concrete pavement for its effective usage for present scenario. Concluding all the test results the replacement of 25% RAP coarse aggregates and 50% RAP fine aggregates giving more strength than normal concrete which can be used for pavement construction.

Effect of Copper Slag and Granite Powder on the Mechanical Properties of Reclaimed Asphalt Pavement Aggregate Concrete

The replacement of natural gravel aggregate with reclaimed asphalt as coarse aggregate would help in reduction of environmental and ecological effects. Researches were rarely performed by replacing fine aggregate in reclaimed asphalt pavement aggregate concrete. This project aims to investigate the feasibility of improving the strength of recycled asphalt aggregate concrete in which recycled asphalt aggregate is used as a partial replacement of coarse aggregate at 30%. Abrasion and attrition technique is used to modify or roughen the surface of RAP aggregates. Granite powder and copper slag are used as a partial replacement of sand at 5, 10, 15, 20 and 25% in Abrasion and attrition Treated Reclaimed Asphalt Pavement Aggregate Concrete (ABTRAPC). Thirty cubes, twenty cylinders and twenty beams of concrete with granite powder and thirty cubes, twenty cylinders and ten beams of concrete with copper slag were made and tested. The 7th and 28th day strengths were found out at these replacements. It was observed that the compressive strength, split tensile strength and flexural strength was found to be maximum at 15% replacement of sand by copper slag. The compressive strength was increased about 29.8% compared to ABTRAPC. Flexural strength similar to normal concrete and about 12.8% greater compared to ABTRAP concrete. The compressive strength and flexural strength was also increased to a maximum at 15% replacement of sand by granite powder and split tensile strength at 20% replacement of granite powder. The results showed that the potential of reclaimed asphalt aggregates as a partial replacement of coarse aggregates in concrete could be effectively enhanced with its a combination with granite powder or copper slag. The increase in compressive strength values and the increase in flexural strength values similar to normal concrete proved that this concrete has its potential to be used in pavement applications.

Laboratory investigation of RAP aggregates for dry lean concrete mixes

In the present study, the suitability of coarse (C) and fine (F) RAP aggregates extracted from two flexible pavements (OLD (O) & NEW (N)) having different service (20 yrs. & 2½ yrs.) and stockpiling life (8 months & 0 months) for productions of Dry Lean Concrete (DLC) and bituminous mixtures is assessed. For the same, a total of 15 DLC mixes were cast, consisting of 9 mixes containing different proportions (25–100%) of CO and CN aggregates and 6 mixes containing FO (25–100%) and FN aggregates (25% and 50%). The effect of both fractions of RAP on optimum moisture content (OMC), maximum dry density (MDD), compressive strength, water absorption and permeable voids were studied. Volumetric properties of compacted bituminous mixes containing aggregates milled from new pavement were also investigated. It was found that aggregates obtained from old pavement have the potential to replace 75% coarse and 50% fine natural aggregates whereas 25% CN and zero FN aggregates may be utilized for DLC mixes. Contrary, aggregates obtained from new pavement were found to be suitable for construction of base and wearing course of flexible pavements whereas aggregates from older pavement could not be even molded while preparing test sample due to loss of binding properties of asphalt mixtures by virtue of oxidation process.