Pavement Aggregates Research Articles

Mechanical Behavior Investigation of Reclaimed Asphalt Aggregate Concrete in a Cold Region.

Recycled construction and demolition (C&D) waste can reduce the rebuild cost, and is environmentally friendly when recycled asphalt pavement (RAP) aggregate constitutes the main part. This paper investigated the mechanical performance of RAP concrete, and the applicability of RAP in road base layers also was discussed. Several mechanical laboratory tests were selected, including the unconfined compressive-strength, splitting-strength, and compressive-resilience modulus tests. The RAP concrete had a good road performance in a cold region, which was proved by the temperature-shrinkage test, dry-shrinkage test, freeze–thaw-cycle test, and water-stability test. Based on various cement dosages from 3.5% to 5.5% in RAP concrete mix design, three RAP aggregate replacement ratios (30%, 40%, and 50%) were selected to study the variation of mechanical properties with increasing curing time, and the optimal aggregate substitute ratio was determined. A scanning electron microscope (SEM) was used to observe the inner-structure interface between the asphalt binder and cement stone. A numerical model is presented to simulate the RAP compressive strength with respect to the effect of multiple parameters. The research results can provide a technical reference for RAP use in the reconstruction and expansion of low-grade highway projects.

Production of Roller Compacted Concrete Made of Recycled Asphalt Pavement Aggregate and Recycled Concrete Aggregate and Silica Fume

Production of Roller Compacted Concrete Made of Recycled Asphalt Pavement Aggregate and Recycled Concrete Aggregate and Silica Fume

Study on the Performance and Adhesion Behavior of Ultrathin Wearing Course Using Calcined Bauxite as Aggregate

An ultrathin wearing course is an effective maintenance treatment for prolonging the service life of asphalt pavements, which have been widely used in the field of pavement construction and road maintenance. However, the repeated vehicle load and wear results in a decreased durability of ultrathin wear course cover pavement. Hence, the gradation of ultrathin wear course was designed using calcined bauxite in this study, and the water stability, low-temperature properties, resistance to permanent deformation, and salt erosion were investigated through a laboratory test. Results indicated that the addition of a nonammonia antistripping agent significantly improves the water stability of the asphalt mixture with calcined bauxite and its ability to resist salt erosion as well as improve its low-temperature deformation ability. At the same time, polyphosphoric acid improves the adhesion between asphalt and calcined bauxite aggregate and the high-temperature performance of asphalt mixture but has limited improvement in water stability and resistance to salt erosion. This research is conducive to the widespread use of calcined bauxite aggregates in road pavements and is of great significance for improving the durability of ultrathin wear course asphalt pavements.

Comprehensive Analysis of Steel Slag as Aggregate for Road Construction: Experimental Testing and Environmental Impact Assessment.

Blast Oxygen Furnace (BOF) slag represents one of the largest waste fractions from steelmaking. Therefore, slag valorisation technologies are of high importance regarding the use of slag as a secondary resource, both in the steel sector and in other sectors, such as the construction or cement industries. The main issue regarding the use of BOF slag is its volumetric instability in the presence of water; this hampers its use in sectors and requires a stabilisation pre-treatment. These treatments are also cost-inefficient and cause other environmental issues. This paper analyses the use of untreated BOF slag from a technical and environmental point of view, suggesting it as an alternative to natural aggregates in road surface layers and asphalt pavements. A comprehensive analysis of the requirements to be met by raw materials used in asphalt mixes was performed, and a pilot test was carried out with two different mixtures: one mix with limestone as coarse aggregate and another with 15% BOF slag. Furthermore, the global warming impacts derived from each mix with different aggregates were measured by Life Cycle Analysis (LCA), and a transport sensitivity analysis was also performed. The results show how the utilization of BOF slag as coarse aggregate in road construction improves the technical performance of asphalt mixtures (Marshall Quotient 4.9 vs. 6.6). Moreover, the introduction of BOF slag into the asphalt mix as a coarse aggregate, instead of limestone, causes a carbon emissions reduction rate of more than 14%.

GEOTECHNICAL PROPERTIES AND AGGREGATE QUALITY ASSESSMENT OF MARL DEPOSIT IN AFIKPO AREA, SOUTHEASTERN NIGERIA

Purpose: Marl is an impure limestone that is generally not good for cement production because of its low calcium carbonate content. Aggregates derived from marl deposit in Afikpo Area, Southeastern Nigeria, are currently being used in construction of concrete structures and highway pavements by construction companies and individuals. There is no published information on the suitability of the aggregates for such uses. The purpose of this study was to determine the suitability of the aggregates as components of concrete and highway pavements in terms of satisfying the non-swelling and acceptable strength characteristics / requirements.
 Methodology: Geotechnical tests including Atterberg limits (liquid limit, plastic limits and plasticity index), linear shrinkage and free swell were used to evaluate the swelling characteristics; while physico- mechanical tests including specific gravity, water absorption. Aggregate Crushing Values (ACV), Aggregate Impact Value (AIV) and Los Angele Abrasion Value (LAAV) were used to evaluate the strength characteristics. The field studies indicate that the marl deposit is associated with Ezeaku Formation of Lower Benue Trough. Results: Results of geotechnical tests indicate liquid limit, plasticity index, linear shrinkage and free swell values of 29.50%, 4.60%, 0.36% and 10.00%, respectively. Similarly, results of physico-mechanical tests indicate specific gravity, water absorption, ACV, AIV and LAAV values of 2.58%, 1.90%. 23.50% 29.45% and 42.70%, respectively.
 Unique contribution to theory, practice and policy: Since the results satisfy the non-swelling characteristics (plasticity index < 12%, linear shrinkage < 8% and free swell < 50%) and acceptable strength characteristics (water absorption < 3%, ACV < 30%, AIV < 30% and LAAV < 45%) requirements for good concrete and highway pavement aggregates, aggregates derived from marl deposit in Afikpo Area, Southeastern Nigeria, are strongly recommended to be used as aggregates in concrete and highway pavement construction.

Stress-strain response analysis of demolition wastes as aggregate base course of pavements

The sustainable construction approach by utilizing recycled aggregates has increasingly been the focus of highway construction industries and local road authorities in recent years. The efficient usage of recycled aggregates for sustainable construction is owed to more than a decade of extensive experimental research aiming to remove uncertainties in the properties and performance of recycled aggregates in transport infrastructures. Nevertheless, a lack of knowledge exists about the stress-strain response of the pavement structures constructed using recycled aggregates. The main goal of this study was to propose a response analysis approach to incorporate the repeated load triaxial (RLT) test results as a Level 1 MEPDG input parameter in a well-established pavement analysis software named FlexPAVETM. In this approach, the aggregate base course was divided into ten sublayers of equal thickness. Three different constitutive resilient modulus (Mr) models were utilized to determine the Mr of each sublayer corresponding to the stress levels achieved at that sublayer. Modeling the pavements in FlexPAVETM by assigning the corresponding Mr to the sublayers resulted in a more accurate stress-strain response compared to the conventional linear elastic analysis approach. This approach provides a more realistic and, accordingly, more accurate analysis of the behavior of unbound aggregates in pavements. The secondary goal of this study was to investigate the stress-strain response of pavements with aggregate base courses made of three types of recycled construction and demolition wastes, being recycled concrete aggregate (RCA), crushed brick (CB), and waste excavation rock (WR). The resilient properties of the demolition wastes were determined through repeated load triaxial (RLT) testing. A typical pavement profile consisting of asphalt surface course, aggregate base course, and an A6 type of natural soil as subgrade was modeled using FlexPAVETM. The response analysis was undertaken following the proposed sub layered approach. Under the loading conditions adopted in this research, with bulk stresses <185 kPa, CB and RCA exhibited a superior Mr response compared to the conventional virgin materials, while WR showed an inferior behavior.

Utilization of tailing waste as aggregate for road pavement

Tailing waste from gold mining in Papua, Indonesia, is a severe problem for the environment. Tailing as Hazardous and Toxic Substances, the deposits so massive. On the other hand, the availability of natural aggregates for road pavement continues to run low. The problems can be solved by utilizing tailing as a road base layer with massively, fulfill specification, and save. The purpose of this research is how to utilize tailing as a road base layer. The research methods used are experiment laboratory method by physical, chemical, TCLP, and mechanical strength test. The physical analysis shows that the size of the tailing is loose and non-cohesive, so it requires binding material to increase bearing capacity. The TCLP test showed that the level of toxic material in tailing was fulfilled the threshold. The stabilization analysis of tailing with 20% clay soil produces CBR 17,3% and can only be utilized as embankment. Stabilization with 13,35% cement fulfills the target UCS 24 kg/cm2 to be used as a road base layer. Marshall test result by 60% tailing and 7% asphalt meet specifications to be asphalt road base layer.

Assessment of the alkali-silica reactivity potential in granitic rocks

The alkali-silica reactivity of granites may significantly affect the durability of road and airfield concrete pavements. The aim of the study was to evaluate the reactivity of granites commonly used as an aggregate in concrete pavements, with particular emphasis on microscopic methods. The research was focused on petrographic diagnosis of reactive minerals in granites, their quantitative analysis and comparison of the obtained results with standard measurements. The strained quartz was recognized as a reactive component and the linear relationship between its content and specimens expansion was found.

Deterioration of modern concrete structures and asphalt pavements by respiratory action and trace quantities of organic matter.

In concrete structures (concrete), damage from cracks, deterioration, amorphization, and delamination occur in some structures, causing disaggregation (concrete changed to very fine particles) and hollowing out of the concrete. In concrete pavements, damage from large amounts of pop-out of aggregate occurs from the surface of the concrete pavement 4-5 hours after spraying of snow melting agent on the surface of the pavement. The damage from disaggregation, blistering, cracks, and peeling-off of a surface course have also been observed in asphalt runways and highways. The damage from disaggregation, cracks and pop-out of aggregate in asphalt pavements and concrete structures have long been seen as strange and unexpected and have defied explanation. As a result of examinations in various experiments, it was concluded that all of the unexplained kinds of damage of both asphalt pavements and concrete structures were caused by Trace Quantities of Organic Matter (TQOM), Air Entrained (AE) water reducing agent in air and/or cement, and surfactant in snow melting agent. The emission sources of TQOM and these organic substances were also identified by chemical analysis for these unexpected and unexplained phenomena. The TQOM includes phthalate compounds (phthalates in the following), amine compounds, phosphate compounds, snow melting agent and Sodium Polyoxyethylene Nonyl phenyl Ether Sulfate (SPNES). SPNES is a surfactant in windshield washer fluid for automobiles. We found that the water content and content of organic matter in damaged asphalt pavements and concrete structures are also important indicators for the damage. Further, a new evaluation method for amorphization was proposed in this study and it appears suitable for evaluating the safety of concrete structures along roads which were exposed to TQOM in severely air-polluted environments.

Research on Mix Design of Cement Stabilized Recycled Aggregate Pavement Base

In this paper, the compaction test of the mixture with different cement content and different replacement rate of recycled aggregate is studied by vibration compaction method. Through the research on the mix design of cement stabilized recycled aggregate pavement base, the optimum content of cementitious materials is determined, and the maximum dry density and optimum water content of each test scheme are obtained. The influence of cement content and recycled aggregate content on the maximum dry density and optimum water content of the mixture is analyzed.

Studies on Strength and Behaviour of Hot Mix Asphalt Using Steel Slag Aggregates in Pavements

Steel slag is a by-product of the steel industry. These waste materials create environmental pollution in the vicinity as they are imperishable and safe disposal of Industrial wastes is a major problem. This made engineers think about wastes that can be helpful for recycling. Based on intensive laboratory testing program, the characteristic properties of Steel Slag Aggregate (SSA) were assessed to determine its suitability to be used in Hot Mix Asphalt (HMA) and also as a potential material to be used as aggregate in flexible pavements. By utilizing this material in construction can minimize the depletion of natural resources around the world. Four different percentages (0%, 25%, 50% and 75%) of SSA were used and the proposed mix designs for HMA were conducted following the Marshall mix design. The experimental results indicate that the addition of SSA has significant improvement in the properties of HMA. An increase in density, stability and flow values and reduction in the per cent of air voids were observed in specimens prepared with above replacements. Keywords: Hot Mix Asphalt (HMA): Steel Slag Aggregate (SSA): Natural Aggregates (NA): Marshall Mix design:

Evaluating the Performance of Wicking Geotextile in Providing Drainage for Flexible Pavements Built over Expansive Soils

The longevity and performance of a pavement section depend on the characteristics of the subgrade soil. A majority of the pavements in North Texas, U.S., are constructed on expansive soils. The deterioration of the pavement performance because of rutting, cracking, and differential heaving is a regular phenomenon in the regions predominantly distributed with expansive soils. The pavements, particularly those built for low-volume traffic conditions, experience distress because of the high swelling and shrinkage characteristics of the underlying problematic soils. Geosynthetics have been traditionally used to improve such poor subgrades because of their many benefits, such as ease of installation, and ample mechanical and hydraulic properties. In the last decade, a newly available wicking geotextile, with a moisture redistribution capacity, has been developed to improve the performance of pavements constructed over expansive and frozen soils. In this study, small-scale laboratory and full-scale field studies were conducted to comprehend the wicking ability of this innovative geotextile in an expansive soil environment. Full-scale test sections were constructed with reclaimed asphalt pavement aggregate and traditional crushed stone aggregates in the base layer near North Texas. Details of the construction and instrumentation procedure are discussed in this paper. A comparative study between the performance of the pavement sections subjected to traffic loads and moisture intrusion was also performed. Furthermore, the rutting life of the sections, estimated using a linear elastic model, was compared and validated using the in situ data. The observations during the initial phase indicated that the wicking geotextile has the potential to improve the long-term pavement performance.

Large-scale direct shear testing of waste crushed rock reinforced with waste rubber as pavement base/subbase materials

Construction and demolition (C&D) waste and scrap tires contribute to huge portions of the waste generated worldwide. One of the most effective and practical ways to eliminate the need to send C&D waste and scrap tires to landfills is to recycle and reuse them in civil and construction projects. On the other hand, the shear behavior of the granular aggregates has a significant influence on the performance of pavement layers. Unbound granular aggregates such as crushed rock have high compressive strength but low tensile strength. One way to improve the aggregates’ tensile weakness is to introduce crumb rubber into the unbound granular materials. This study explored the possibility of using the blends of waste crushed rock (WCR) and waste rubber, as a low-carbon and economically viable solution, for pavement base/subbase application. Little research has been done to study the shear strength properties of mixed waste materials. This study is the first to evaluate the shear behavior of WCR reinforced by varying sizes & percentages of waste rubber using a large direct shear testing (LDST) device. The experimental results show that an introduction of waste rubber to WCR increased the shear capacity of the blends. Mixtures of WCR with rubber in two sizes (coarse/fine) and at three distinct percentage inclusions (0.5, 1 and 2%) all satisfy the shear strength requirements for aggregates in pavement base/sub-base applications. In addition, a straightforward non-linear model was developed in order to facilitate easy estimation of the shear capacity of rubberized WCR. The outcomes of this study can provide practical guidance on the application of rubberized waste crushed rock as pavement base/subbase materials.

Influence of UV-modified GTR on the properties of interlocking concrete paving units

This work studies the impact of tire rubber on interlocking concrete paving units for application in roads or storage areas by adding ground tire rubber (GTR) as a treated and recycled aggregate. The rubberized concretes are fabricated by replacing the fine aggregate with GTR in 5, 10, 15, and 20% (V/V). The compressive strength decreased by 56.03% after replacing 20% of the fine aggregate by GTR. The replacement of the GTR did not exhibit a significant change in the water absorption values that increased only 0.85% when replacing up to 20% of GTR in the concrete and the resultant impact resistance increased by more than 360% if compared to the conventional concrete. Combining the beneficial and potential environmental impact of finding new destinations of GTR with the outstanding enhancement of the impact resistance of GTR-modified concretes highlights this type of material as a promising recycled aggregate in pavement and even structural applications that require this property.

Clogging in Pervious Concrete Pavement Made with Non-conventional Aggregates: Performance Evaluation and Rehabilitation Technique

This paper presents the clogging nature of a pervious concrete pavement using non-conventional aggregates. In order to mitigate the shortage of construction materials, brick aggregate has been preferred by many researchers as an efficient alternative to the natural stone aggregates. But the application of brick aggregate in the pervious concrete pavement is a new concept and the clogging behaviour of the pervious concrete made with waste over-burnt brick is still unknown. In this study, laboratory tests are carried out through small-scale and large-scale model tests to explore the effects of various design variables in the clogging pattern. All the experimental results are validated with the statistical analysis, and a prediction model is developed to understand the clogging nature which can be further used for modelling the clogging behaviour of a pervious concrete pavement. The rehabilitation of pavement performed through pressure washing indicated a significant improvement in the permeability after de-clogging.

Segmentation of Aggregate and Asphalt in Photographic Images of Pavements

Particle size distribution of aggregate in asphalt pavements is used for determining important characteristics like stiffness, durability, fatigue resistance, etc. Unfortunately, measuring this distribution requires a sieving process that cannot be done directly on the already mixed pavement. The use of digital image processing could facilitate this measurement, for which it is important to classify aggregate from asphalt in the image. This classification is difficult even for humans and much more for classical image segmentation algorithms. In this paper, an expert committee approach was used, including classical adaptive Otsu, k-means vector quantization over a set of 8 principal components obtained from 26 features, and a Gaussian mixture model whose parameters are estimated through the expectation-maximization algorithm. A novel cellular automata approach is used to coordinate these expert opinions. Finally, a simple heuristic is used to reduce sub- and over-segmentation. The segmentation results are comparable to those obtained by a human expert, while the sieve size of the segmented images corresponds very well with that obtained from the sieving process, validating the proposed method of segmentation. The results show that with the digital imaging procedure it was possible to detect particles with a size of 100 m with 90% of success with respect to time-consuming manual techniques. In addition, with these results it is possible to establish the homogeneity of the sample and the distribution of the particles within the asphalt mixture.

Rutting Resistance of Hot Mix Asphalt Containing Coarse Recycled Concrete Aggregates Coated with Waste Plastic Bottles

The use of recycled concrete aggregate (RCA) as a part of coarse aggregates in asphalt pavements confers economic and environmental benefits. Coarse RCA (CRCA) has inferior mechanical and physical properties compared to natural aggregates due to very porous and weakly adhered cement mortar. In this study, CRCA surfaces were coated with waste plastic bottles (WPB) and used at 15%, 30%, and 50% in the asphalt concrete. The Marshall, stiffness modulus, and dynamic creep tests were performed to determine the strength of hot mix asphalts against rutting. The results revealed that the use of untreated CRCA reduced the Marshall quotient and the rutting resistance of the asphalt concrete. The results of the stiffness modulus and dynamic creep tests indicated that CRCA incorporation increased permanent deformation in the tested specimens due to the reduction of asphalt concrete stiffness. However, the asphalt concrete containing treated CRCA had lower permanent deformation because WPB promotes CRCA stability by penetrating its void and reinforcing cement mortar. Furthermore, by raising the temperature, the strength of all asphalt concretes decreased against rutting, and the reduction rate was higher in the modified specimens.

Performance Characteristics of Road-base Containing Mixed Steel Slag and Cathode Ray Tube Glass

One way to promote sustainability in construction is through the preservation of natural resources and utilization of recycled wastes. This paper describes a laboratory study on the use of steel slag and cathode ray tube (CRT) glass for road base pavement layer. Measurements of the physical and mechanical characteristics of each sample are taken to evaluate the effectiveness of using these materials in road base pavements. The laboratory evaluation comprised of Los Angeles abrasion value (LAAV) test, California bearing ratio (CBR) test and performance characterization; the unconfined compression strength (UCS) and indirect tensile strength (ITS) tests were also performed. The values for LAAV are satisfactory, indicating that the steel slag and granite mixtures have adequate resistance and abrasion for use as road base pavement aggregates. The higher percentages of steel slag in the mixture produced higher CBR values for both the soaked and unsoaked mixtures. Test results also show that the mixtures containing up to 70% steel slag and 15% CRT glass meet the standards requirements. Results of the UCS and ITS tests for performance characterization showed that the performance of the sample mixture was enhanced significantly upon incorporating a higher percentage of steel slag in the mixture. The lab test results showed that the mixture composing of granite, steel slag and CRT glass is a suitable alternative made from recyclable materials, for use in road base pavement layer.

Preparation of organic montmorillonite promoter for improving the adhesion between bitumen and acidic aggregate

The utilization of acidic aggregate in asphalt pavement has become a research focus in recent years. The present work aims to prepare organic montmorillonite (OMT) as an adhesive promoter to improve interfacial adhesion between bitumen and acidic aggregate. The preparation method of OMT was optimized by parallel experiments. The prepared OMT was characterized by microscopic technologies, including TG, XRD, FTIR, SEM-EDS and TOC. Conventional bitumen tests were carried out to evaluate the performance of bitumen with different dosages of OMT. The adhesion between aggregate and bitumen was performed by using zeta potential, pull-off test and boiling water test. The results show that the optimized preparation method of OMT is of feasibility. The surface functionalization of OMT includes intercalated and grafted organification. OMT is a promising promoter for maintaining the conventional properties of bitumen. OMT particles have positive charge, which enhances the adhesion effect between bitumen and acid aggregates. After addition of 5.0% OMT, the fracture energy and peak load of bitumen were significantly increased, and the coating degree of acid aggregate after boiling water test was also improved. From a cost and optimal performance perspective, the optimized dosage of OMT promoter was 5.0% by weight of the bitumen, which has a better adhesion compared with neat bitumen.

Reclaimed Asphalt Pavement as a Substitution to Natural Coarse Aggregate for the Production of Sustainable Pervious Concrete Pavement Mixes

AbstractThis study discusses the effect of utilizing coarse reclaimed asphalt pavement (RAP) aggregates as a replacement to natural coarse aggregates (NCAs) for the production of pervious concrete ...