Aggregate Blends Research Articles

Aggregate blending optimisation in quarries to improve of the mechanical and environmental properties of concrete

ABSTRACT In this study, concrete mix optimisation was carried out with materials provided by Catalca (Ca) and Cendere (Ce) quarries in the region of Istanbul, Turkey which produce concrete aggregate from different rock formations. Accordingly, the properties of six different concrete aggregates produced from these quarries (3 regions in Catalca quarry and 3 regions in Cendere quarry) and the amounts of CO2-e released into the atmosphere by producing these aggregates were determined. Then, these aggregates were used in different proportions in concrete mixtures and the effects of aggregate types on the mechanical properties of concrete were statistically demonstrated by the experimental design method. According to the results, the mechanical properties of concrete were statistically significantly affected by the use of aggregate in different formations. In addition, empirical approaches that can be used in estimating the compressive strength, tensile strength and elasticity modulus of concrete have been found and using these approaches, mixtures that maximise these mechanical properties of concrete have been determined. Accordingly, mechanical properties of concrete were maximised in mixtures where Ca 1st Region 25% - Ca 2nd Region 75%, Ca 1st Region 60% - Ca 3rd Region 40%, Ca 2nd Region 13% - Ca 3rd Region 87%, Ce 1st Region 10% - Ce 3rd Region 90%, Ce 1st Region 63% - Ca 2nd Region 37%, and Ca 1st Region 35% - Ca 2nd Region 5% - Ca 3rd Region 60% were used. The CO2-e values of these mixtures were calculated as 8.405, 8.248, 8.529, 8.630, 8.476, and 8.365 kg/t respectively.

Development of aggregate gradation based on asphalt film thickness and aggregate structure

This study is an attempt to make the aggregate blending methodology, used during the mix design process of asphalt mixture, independent of control points. The proposed procedure involves optimization of aggregate gradation based on the concept of apparent asphalt film thickness (AAFT) and balance within the aggregate structure. The underlying hypothesis was validated by comparing the volumetrics and performance of asphalt mixtures, prepared using two generated aggregate gradations, with a control asphalt mixture. The results indicated that the generated aggregate gradations had similar rutting, fatigue, and moisture sensitivity properties to the control mix. Three field trial sections were laid using the proposed procedure. Preliminary investigation revealed comparable to better density and Marshall characteristics than the conventional mixture. It is envisaged that the results and discussions from the present study can be used with the approach of balanced mix design for choosing an aggregate gradation with desirable performance attributes.

Novel base predictive model of resilient modulus of compacted subgrade soils by using interpretable approaches with graphical user interface

The flexible pavement system consists of layers that are made up of a blend of aggregates and bitumen. To design flexible pavement systems that are both safe and environmentally sustainable, it is essential to have an accurate understanding of the resilient modulus (Mr) of the compacted subgrade soil. Mr refers to the ability of the soil to resist deformation under repeated loads. Thus, a critical parameter affects the performance and longevity of pavement systems. This study employs machine learning (ML) algorithms such as individual and ensemble learners using an extensive database of 2813 data points. These include dry unit weight, weighted plasticity index, confining stress, deviator stress, moisture content, and the number of freeze-thaw cycles (FT). The individual or weak learners were incorporated to create strong and robust ensemble learners by employing techniques such as bagging, adaptive boosting, and random forest (RF). Ensemble learning methods were used to improve the performance of individual learners, such as support vector machine (SVM) and decision tree (DT), by combining their predictions. To achieve the highest R2 value, a total of twenty bagging and boosting sub-models were trained and optimized. The validation of the test data was carried out through K-Fold cross-validation, utilizing metrics such as R2, MAE, and RMSE. The developed models were rigorously tested using statistical indices (MAE, MSE, RMSE, and RMLSE) to verify their predictive accuracy, reliability, and trustworthiness. The findings indicate that the integration of bagging and boosting techniques improves the efficiency of individual machine learning (ML) models. The combination of RF and DT utilizing bagging resulted in the most reliable performance, achieving an R2 value of 0.9 and demonstrating minimum errors. In general, the implementation of the ensemble algorithm in ML improved the overall prediction accuracy of the model. Sensitivity analysis reveals that the prediction of the resilient modulus (Mr) of the subgrade is primarily influenced by dry density, confining stress, and deviator stress. Moreover, a graphical user interface (GUI) is developed for practical implantation.

Performance of optimized composition of epoxy resin adhesive used in High Friction Surface Treatment

The High Friction Surface Treatment (HFST) paving technique is widely employed in engineering practices globally, serving to enhance the long-term anti-skid performance of pavements. However, there still exist significant gaps in research regarding the modified and optimized composition and corresponding content of the polymer binding materials used in HFST, as well as the performance of the pavements laid with modified and optimized blended aggregates during service. To address these issues, this research first modified and optimized the composition ratio of traditional epoxy resin materials. Subsequently, a toughened, high-flow epoxy bonding system suitable for the maintenance of concrete pavements was prepared. Additionally, the study explored the bonding performance of this system with both the cement base surface and aggregates. The results established that the optimal ratio range for the modified epoxy adhesive system is E51 epoxy resin to curing agent to toughening agent to diluent in the proportions of 100: 30–35: 20–30: 5. The experimental group used a high-flow epoxy resin adhesive ratio of E51 epoxy resin: curing agent: toughener: diluent = 100:30:20:5. For control group 1, the ratio of epoxy resin adhesive was E51 epoxy resin: curing agent = 100:30, and for control group 2, the ratio was E44 epoxy resin: curing agent = 1:1. Compared with control groups 1 and 2, the modified epoxy system with the cement base demonstrated a 149 % increase in average pull-off strength and an 18 % increase in average shear strength. Similarly, in comparison with control groups 1 and 2, the modified epoxy system with aggregates exhibited a 174 % increase in average pull-off strength and a 541 % increase in average shear strength. Based on the pull-off and shear test results, it was ultimately determined that the dosage of modified epoxy binder for HFST mixtures should be controlled at 1.0–1.2 kg/m2, and the dosage of aggregate should be controlled at 3.3–4.3 kg/m2. These findings provide valuable insights into optimizing HFST pavement compositions for improved performance and longevity.

Tackling P3HT:Y‐Series Miscibility Through Advanced Processing for Tunable Aggregation

AbstractPolymer and small molecule blend thin films are of strong interest for organic electronics and particularly organic solar cells. The high miscibility in blends of ordinary P3HT and state‐of‐the‐art Y‐series non‐fullerene acceptors (NFAs) suppresses phase separation and aggregation challenging successful charge separation and transport. In a recent work, current‐induced doping (CID) is introduced, a method to precisely control the aggregation of Poly(3‐hexylthiophene) (P3HT) in solution. The highly ordered pre‐aggregation in solution is used here to control the P3HT aggregation in neat films and blends with Y12 (BTP‐4F‐12). This results in a 25‐fold increase in hole mobility in P3HT organic field‐effect transistor (OFET) devices and tunability of the P3HT aggregate quality in the presence of Y12 over large ranges. At the same time, particularly the Y12 long‐range ordering is heavily suppressed by increasing P3HT aggregation. However, solvent vapor annealing (SVA) leads to an extraordinarily high Y12 ordering, changes in the crystal orientation of Y12, and a further improvement of P3HT aggregation. A broad range of different degrees of aggregation of both materials can therefore be obtained in the final thin films solely by changing processing parameters without changing the composition of the material system.

Impact of Nonrecyclable Plastics on Asphalt Binders and Mixtures

Low-density polyethylene (LDPE) and polystyrene (PS) were evaluated for incorporation as binder additives to enhance the potential performance of asphalt concrete (AC) mixtures, as well as addressing global rising concerns over nonrecyclable plastics accumulation. Incorporation of LDPE and PS in asphalt binder resulted in an increase in its complex moduli over a range of temperatures and frequencies, as determined using frequency sweep (FS) and linear amplitude sweep (LAS) tests. AC performance tests were conducted, including the Hamburg wheel-tracking test (HWTT) to assess potential rutting, the Illinois flexibility index test (I-FIT) to determine cracking potential, the indirect tensile strength test (ITS) to assess moisture susceptibility, and the dynamic modulus for structural capacity. Two control AC mixes were designed, utilizing aggregates from different sources. For each AC mix, the aggregate blend and binder content were kept constant, with only the binder type changed. LDPE and PS were added through a wet process in one mix. Dry and wet processes were used in the other mix. Waste plastics–modified AC mixes, in both wet and dry processes, exhibited reduced rutting potential. However, the cracking potential and moisture damage susceptibility varied, depending on the modified AC mix. The addition of waste plastics had no impact on AC dynamic modulus. The results for waste plastics–modified AC mixes were compared with those for styrene-butadiene-styrene (SBS)–modified AC mixes. While waste plastics modification provided improvement over the control mixes, the performance fell short of that of the double-pump SBS-modified mix.

Using Color Measurements to Quantify Aggregate and Asphalt Emulsion Compatibility

The compatibility of asphalt emulsion and aggregate plays a significant role in the aggregate retention performance of chip seals. There are several, similar standardized test methods available for assessing the compatibility of emulsion–aggregate blends, including AASHTO T 59, ASTM D244, and North Carolina Department of Transportation (NCDOT) A-24. In all methods, a sample of aggregate and emulsion is mixed and rinsed. Subsequently, the compatibility of the rinsed sample is reported as “good,”“fair,” or “poor” based on visual inspection of asphalt coating the aggregate surface area. These visual inferences are subjective, making them susceptible to potential operator bias. The aim of this study is to develop an objective means to quantify emulsion–aggregate compatibility by using the Asphalt Compatibility Tester to obtain color-based measures in lieu of the visual assessment procedures. Multiple aggregate sources (granite, limestone, and lightweight), emulsion types (CRS-2L, CRS-2, and SS-1h), and sources were evaluated. In total, 25 emulsion–aggregate blends were analyzed. The results were used to establish color index thresholds to capture good- versus fair- or poor-performance emulsions. Additionally, chip seal samples from five construction projects were subjected to the Vialit test to measure aggregate retention performance. The Vialit test results were compared with the compatibility test results as a preliminary evaluation of the color-based criteria proposed here. The results indicated that the NCDOT A-24 procedure coupled with color measurements is effective at capturing the compatibility of emulsion–aggregate blends, providing a potential means to remove the subjectivity of the current visual rating procedures.

Mechanical Characteristics of Environmentally Friendly Permeable Pavement: Enhanced Porous Asphalt

This study explores the mechanical properties of porous-asphalt pavement, focusing on the influence of various polymers (elastomeric and reactive elastomeric terpolymers) and different aggregate compositions. Two aggregates were utilized: one is exclusively limestone-based and the other is a blend of limestone and basalt aggregates. The research findings unveiled that mixtures containing the conventional bitumen failed to meet the Cantabro loss-test criterion required for porous asphalt, necessitating a maximum threshold of 20%. In contrast, asphalt mixtures modified with polymers exhibited notably superior performance, particularly in terms of permeability, Cantabro loss and the ratio of indirect tensile strength. These results underscore the significant impact of polymer modification on enhancing the crucial mechanical properties of porous asphalt. Therefore, the study suggests the adoption of polymer-modified asphalt as a viable strategy to improve pavement longevity and overall performance, promoting its use for sustainable and durable infrastructure. Keywords: Porous asphalt, Permeability, Modified porous asphalt, Porous-asphalt design, Polymer modification, Cantabro loss.

Effect of compaction degree on the topological characteristics of force chain network (FCN) in aggregate blend

Aggregates are the main carrier to resist external loads for asphalt pavement, and the characteristics of force chain network (FCN) in aggregate blend are closely related to the skeleton performance of asphalt mixture. This study analyzed the effect of compaction degree of aggregate blend on the topological characteristics of FCN using discrete element (DEM) and complex network theory. Six types of aggregate blends with different gradations were generated and compacted using DEM software EDEM. The compaction degree was evenly divided into 7 parts from the loose to the compacted states. FCN topology graph (FCNTG) of aggregate blend at each compaction degree was built according to the contact information between aggregates and the definition of complex network. The features of each FCNTG were quantified using the indicators characterizing complex network (including degree, vertex strength, clustering coefficient, and path length). The effect of compaction degree on the characteristics of FCN was analyzed. The results showed that complex network theory is a feasible method for investigating aggregate blend FCN. Each topological feature indicator in complex network method can be used to analyze the internal structural features of aggregate blend. With increasing compaction degree, the average degree and the average vertex strength of aggregate blend FCN and different size particles increase gradually, the clustering performance of particles becomes better gradually, and the average path length of FCN decreases gradually. There is a good linear relationship between the compaction degree and each topology indicator except the vertex strength. The compaction can reduce the dispersion degree of the contact forces between particles in aggregate blend and make it more uniform. It can also shorten the path length between two particles, which is important to improve the efficiency of transferring the external load.

Field Performance Evaluation of Recycled Aggregate Blends Used for Backfilling Deep Excavated Trenches

Field Performance Evaluation of Recycled Aggregate Blends Used for Backfilling Deep Excavated Trenches

Sustainable application of industrial side streams as alternative fine aggregates for cement mortar

Increase in industrialization has led to the production of huge volume of side-stream materials that need safe disposal solutions. The present study proposes the use of local industrial side streams such as ferrochrome slag, phyllite dust and mine tailings as secondary raw materials for construction, mainly as fine aggregates. Four different cement mortar mixtures, with a combination of selected side streams as a sole, binary, and ternary blends were investigated. Workability, strength, and durability properties of the derived mortar mixtures were compared with mortar produced using standard sand as reference. Mortar mixtures with a ternary blend of side-stream fine aggregates resulted in a compressive strength of 68–72 MPa at 28 days, which is 30–40% higher than that of control mix. The addition of industrial side streams resulted in a denser microstructure and enhanced the mechanical properties. The durability performance of the mortar with alternative fine aggregates is comparable with those of standard sand.

Experimental Investigation of Mechanical and Electromagnetic Performance of Asphalt Concrete Containing Different Ratios of Graphite Powder as a Filler to be Potentially Used as Part of Wireless Electric Roads

This study experimentally investigates the usability of asphalt concrete pavement containing five different ratios of graphite powder (0%, 1.25%, 2.5%, 3.75% and 5% by weight of the aggregate blend or 0%, 25%, 50%, 75% and 100% of the filler content) as a filler to be potentially used as part of wireless electric roads (ER). As part of the study, first, optimum asphalt binder content for the asphalt mixes without graphite powder was determined as 5%. Then, using the determined optimum asphalt binder content, asphalt mixes containing five different ratios of graphite powder as a filler were prepared and their mechanical and volumetric properties based on Marshall mix design methodology were evaluated. As graphite powder ratios in the asphalt mixes increased, their Marshall stability, flow, voids filled with asphalt and unit weight test results mostly decreased but their air content and voids in mineral aggregate test results increased. Possible reasons for this could be: (1) lower bulk specific gravity of graphite powder, (2) higher asphalt absorbance, (3) having greater surface area compared to that of limestone filler, and (4) weak bonds between sheet-like graphite layers. Furthermore, another batch of asphalt mixes containing five different ratios of graphite powder were prepared and tested in the frequency range of 3–18 GHz for their electromagnetic permittivity properties. It was observed in this study that, except for the specimens with 100% graphite powder ratios, transmission magnitudes of all specimens were above 50% up to 8 GHz, indicating that they had comparably high transmission magnitudes so as comparably low tangent loss values. In the frequency range of 3–13 GHz, transmission magnitudes of the specimens with 25% and 50% graphite powder ratios were consistently higher than that having no graphite powder, the ones with 25% powder ratios had the highest transmission magnitudes in most of the cases in this frequency range. Considering the mechanical, volumetric and electromagnetic property test results of the asphalt mixes with five different ratios of graphite powder, it can be concluded that the use of 25% graphite powder ratio (corresponding to 1.25% of the aggregate blend used in the mixes), has a comparably lower negative effect on mechanical and volumetric properties of asphalt mixes and has a positive effect on electromagnetic permittivity properties of asphalt mixes. Asphalt mixes produced with this graphite powder ratio can be considered to be used as part of wireless ER.

Experimental Investigation of Mechanical and Electromagnetic Performance of Asphalt Concrete Containing Different Ratios of Graphite Powder as a Filler to be Potentially Used as Part of Wireless Electric Roads

This study experimentally investigates the usability of asphalt concrete pavement containing five different ratios of graphite powder (0%, 1.25%, 2.5%, 3.75% and 5% by weight of the aggregate blend or 0%, 25%, 50%, 75% and 100% of the filler content) as a filler to be potentially used as part of wireless electric roads (ER). As part of the study, first, optimum asphalt binder content for the asphalt mixes without graphite powder was determined as 5%. Then, using the determined optimum asphalt binder content, asphalt mixes containing five different ratios of graphite powder as a filler were prepared and their mechanical and volumetric properties based on Marshall mix design methodology were evaluated. As graphite powder ratios in the asphalt mixes increased, their Marshall stability, flow, voids filled with asphalt and unit weight test results mostly decreased but their air content and voids in mineral aggregate test results increased. Possible reasons for this could be: (1) lower bulk specific gravity of graphite powder, (2) higher asphalt absorbance, (3) having greater surface area compared to that of limestone filler, and (4) weak bonds between sheet-like graphite layers. Furthermore, another batch of asphalt mixes containing five different ratios of graphite powder were prepared and tested in the frequency range of 3–18 GHz for their electromagnetic permittivity properties. It was observed in this study that, except for the specimens with 100% graphite powder ratios, transmission magnitudes of all specimens were above 50% up to 8 GHz, indicating that they had comparably high transmission magnitudes so as comparably low tangent loss values. In the frequency range of 3–13 GHz, transmission magnitudes of the specimens with 25% and 50% graphite powder ratios were consistently higher than that having no graphite powder, the ones with 25% powder ratios had the highest transmission magnitudes in most of the cases in this frequency range. Considering the mechanical, volumetric and electromagnetic property test results of the asphalt mixes with five different ratios of graphite powder, it can be concluded that the use of 25% graphite powder ratio (corresponding to 1.25% of the aggregate blend used in the mixes), has a comparably lower negative effect on mechanical and volumetric properties of asphalt mixes and has a positive effect on electromagnetic permittivity properties of asphalt mixes. Asphalt mixes produced with this graphite powder ratio can be considered to be used as part of wireless ER.

A Review on Utilization of Steel Slag in Bituminous Concrete

Abstract: The utilization of steel slag in bituminous mixes has been gaining popularity due to environmental concerns and the potential for cost savings. However, it's essential to manage steel slag properly to prevent environmental and health hazards. To control the impact of steel slag, various efforts have been undertaken. Bituminous concrete performance is influenced by factors like binder grade and the aggregate blend. While numerous studies have examined steel slag's performance in bituminous concrete, there is still a need of more research on optimal mix design. Typically, the ideal quantity of steel slag in bituminous mixes falls within the range of 10% to 15%. It's crucial to thoroughly understand the effect of steel slag on the mechanical properties of the mix, often measured using Marshall Stability Test. In India, there hasn't been extensive work on varying percentages of steel slag in bituminous concrete and its resistance against stripping, despite numerous studies on the properties of steel slag aggregates. This paper aims to consolidate the research studies on the enhancements in bituminous mix properties by partial replacement with steel slag, as well as exploring the potential benefits of incorporating steel slag in bituminous concrete mixes.

Modeling the Dynamic Behavior of Recycled Concrete Aggregate-Virgin Aggregates Blend Using Artificial Neural Network

Construction and demolition waste (CDW) aggregates have increased as a result of the rise in construction activities. Current research focuses on recycling of CDW to replace dwindling natural aggregates but pays little attention to permanent deformation behavior due to the anisotropic nature of the blended CDW aggregates. Accordingly, this study performs repeated load triaxial tests to evaluate the permanent deformation mechanism of the blended materials under various shear stress ratios and moisture conditions. An artificial neural network (ANN) deformation prediction model that accounts for the complex nature of the blended CDW and natural aggregate was developed. Moreover, a sensitivity analysis was performed to determine the relative importance of each input variable on the deformation. The results indicated that the shear stress ratio and confining pressure profoundly influence the deformation. It was demonstrated that the proposed prediction model is more robust than the conventional one. The sensitivity analysis revealed that the number of loading cycles, confining pressure, and shear stress ratios are the principal factors influencing the permanent deformation of the blended aggregates with sensitivity coefficients of 31%, 25%, and 21%, respectively, followed by the CDW and moisture contents. This model can assist practitioners and policymakers in predicting the permanent deformation of CDW materials for unbound pavement base/subbase construction.

Cement and fly ash-treated recycled aggregate blends for backfilling trenches in trafficable areas

The shortage of natural aggregates available for filling excavated pipeline trenches in trafficable areas has prompted the exploration of alternative resources. This study investigates the feasibility of using cement and fly ash-treated recycled aggregates as trench backfill materials subjected to traffic loadings. Blends of recycled glass (RG), plastic (RP), and tire (RT) were treated with different proportions of cement and fly ash, resulting in a total of 8 treated blends. Geotechnical tests including compaction and California Bearing Ratio (CBR) were conducted to evaluate the mixtures according to backfill specifications. Specialized pavement testing, such as repeated load triaxial testing (RLT) and quick shear, simulated real-life stress levels at trafficable areas. Scanning electron microscope (SEM) images were taken to investigate the microstructural characteristics of the cement and fly ash-treated samples. The results showed that the CBR and resilient modulus of the treated blends improved with higher cement, fly ash, and RG contents, while they decreased with increased RT content. Cement-treated blends demonstrated significant improvements in peak shear strength with increased cement and RG contents and decreased RT content. Fly ash-treated blends showed minor improvement in peak shear strength when the fly ash, RG, and RT contents varied. Only cement-treated blends exhibited properties comparable to Class 4 (CL4) crushed rock, which was the control material. Under the same stress levels, cement-treated blends demonstrated up to 1.17 and 2.62 times greater stiffness than CL4 and clay subgrades, respectively. The SEM analyses confirmed that the inclusion of cement in the recycled blends resulted in the formation of greater bonds between particles compared to fly ash, which led to higher strength. These findings highlight the potential of sustainable materials in backfilling pipeline trenches under traffic loadings, reducing the reliance on natural aggregates for this application.

Recycled aggregate blends for backfilling deep trenches in trafficable areas

Limited supplies of natural aggregates for backfilling pipeline trenches in trafficable areas have led to considering secondary resources. Utilizing blends entirely made of recycled aggregates to backfill excavated trenches in trafficable areas is rare if any, where traditionally, natural crushed rock has been used. In this study, 18 blends of various proportions of recycled glass (RG), plastic (RP), tire (RT), and concrete aggregate (RCA) were proposed and studied as alternatives. First, typical pavement tests such as compaction and CBR were carried out to select 7 suitable mix designs based on available backfill specifications. The shortlisted blends were further investigated through a specialized testing program, in particular, repeated load triaxial to simulate site stress levels. The results showed that CBR and resilient modulus characteristics improved by the increase in RCA content and the reduction in RT content. Three recycled material blends were selected as the optimum mix designs, and were next compared with the surrounding natural clay subgrades of the study area. The resilient modulus response of optimum mix designs exhibited up to 1.6 times greater stiffness compared to the clay subgrades under the same stress levels. The outcomes of this study reduce the demand for natural aggregates and promote the use of sustainable materials for backfilling pipeline trenches located under traffic loadings.

Characterizing force-chain network in aggregate blend using discrete element method and complex network theory

The force chain network in aggregate blend indicates load transfer path and is the main carrier to resist external loads. The objective of this study is to analyze the force chain network characteristics of aggregate blend on the basis of complex network theory. The virtual aggregate blend models with three stone matrix asphalt (SMA) gradations and three dense asphalt concrete (AC) gradations were constructed using discrete element method (DEM). The force chain network topology structure of each aggregate blend was established according to the aggregate contact parameters extracted from DEM software and the introduced complex network theory. The characteristics of each force chain network were analyzed by the various network evaluation indicators. The results showed that there are two or more contacts between most particle pairs. The average coordination number and the average contact number of aggregate blend are not equal. The degree distribution of each gradation shows a good power-law distribution. The force chain network of aggregate blend is a scale-free network. Big particles have greater average strength and smaller average weight distribution difference compared with small particles. The reference lower limit has better clustering performance for SMA-16, and the reference upper limit has better clustering performance for AC-25. The average path length of SMA-16 is longer than that of AC-25, indicating that SMA-16 has better load transfer ability and skeleton properties.

Anti-skid durability of porous drainage asphalt mixture based on discrete element

In order to improve safety indicators such as the skid resistance and durability of road, the discrete-element method is used to study the proportion of the asphalt mixture, and the spatial structure of the coarse aggregates and asphalt mortar are compared and analysed. Relevant models are established to compare their pendulum values and structural depth attenuation. When the fine aggregate is limestone and the surface polishing times do not exceed 3500 times, the 7/3S1 asphalt mixture has the best pendulum value. However, as the polishing times continue to increase, the mixture ratio also changes. Compared with the 7/3S1 asphalt mixture, the 8/2S1 asphalt mixture has better effect. When the fine aggregate is replaced by limestone, no matter what form the coarse aggregate is, the pendulum value has been improved to a certain extent comparing with the previous mixture. A2S2, 5/5S2, 7/3S2 and 8/2S2 blends, compared with A2A2, 5/5A2, 7/3A2 and 8/2A2 blends, the pendulum value was increased by 1.7, 0.5, 2.3 and 2.1%, respectively. The study shows that in different proportions of coarse aggregates, as the surface texture richness of the blended aggregate increases, the differences between the aggregates also increases, and skid resistance and durability are also enhanced. The research results provide a blending method to increase the skid resistance and durability of asphalt pavement.

Field Performance Evaluation of Base Course Constructed with Reclaimed Asphalt Pavement and Virgin Aggregate Blends

Abstract This study presents the results of four years of data collection from a test site that is constructed as part of an actual roadway. The focus of the study was to evaluate the possibility of achieving similar or better performance characteristics from base course sections constructed with reclaimed asphalt pavement (RAP) blends compared to sections with 100 % virgin aggregate (VA). Two base course sections were constructed by blending VA with 20 % RAP and two with 30 % RAP (four RAP-VA sections). Blends were achieved using fine processed RAP with two different average binder contents (4.9 and 5.6 %). Additionally, two sections were constructed with 100 % VA for comparison. During construction, strain gauges were embedded into the asphalt and base course layers. Long-term performance evaluations were monitored based on data from the strain gauges and in situ testing. Falling weight deflectometer and light weight deflectometer tests were used to evaluate modulus values, and the results showed that all sections constructed with RAP-VA blends had equal or greater modulus values than the 100 % VA sections. International roughness index tests coupled with data from strain gauges were used to evaluate deformations. The results showed that three of the four RAP sections had deformations close to or less than 100 % VA sections (desired outcome). The only exception was in the section constructed with 30 % RAP with lower binder content (4.9 %). Findings from this study showed that field evaluations require multiple methods of testing, and modulus-based measurements alone should not be relied on for performance evaluations. This study demonstrated that it is possible to design base course sections with RAP that perform similar to or better than 100 % VA. A proper blend requires the gradation and binder content of RAP to be characterized and the percentage of RAP blended with VA to be determined based on these properties.