HIGH AIR-VOID VOLUME IMPLICATIONS FOR ASPHALT CONCRETE SERVICE-LIFE AND PRICE PENALTY

In road industry, the construction of asphalt concrete layers is a dynamic process that, if not properly done, will lead to problems compromising the pavement performance. One of the most common problems is poor compaction leading to air-void volume above the maximum acceptable. This study discusses the impact of compaction/density deficiencies and presents an innovative model to calculate the asphalt pavement service-life loss in a simple and objective way, and in line with the road construction managers needs to calculate price penalty for contractors. The model was optimized for dense graded asphalt concrete, that typically has a maximum acceptable air‑void volume between 4% and 7%

Moisture susceptibility of high and low compaction dry process crumb rubber modified asphalt mixtures

The field performance of dry process crumb rubber-modified (CRM) asphalt mixtures has been reported to be inconsistent with stripping and premature cracking on the surfacing. One of the concerns is that, because achieving field compaction of CRM material is difficult due to the inherent resilient nature of the rubber particle, nonuniform field compaction may lead to a deficient bond between rubber and bitumen. To assess the influence of compaction, a series of CRM and control mixtures was produced and compacted at two levels: 4% (low, optimum laboratory compaction) and 8% (high, field experience) air void content. The long-term durability, in regard to moisture susceptibility of the mixtures, was assessed by conducting repeated moisture conditioning cycles. Mechanical properties (stiffness, fatigue, and resistance to permanent deformation) were determined in the Nottingham Asphalt Tester. Results indicated that compared with conventional mixtures, the CRM mixtures, regardless of compaction effort, are more susceptible to moisture with the degree of susceptibility primarily depending on the amount of rubber in the mixture, rather than the difference in compaction. This behavior is different from that of conventional mixtures in which, as expected, poorly compacted mixtures were found to be more susceptible to moisture than were well-compacted mixtures

Creep Performance ofVarious Bituminous Mixtures

Creep is a failure mode, used to describe the tendency of a material to move or to deform permanently to relieve stresses. An example of permanent deformations is rutting, which is caused by repetitive traffic loading that exceeds the ability of the pavement structure to maintain its original profile. Aggregate's particle size distribution, or gradation, is one of the most influential characteristics in the creep performance analysis. Aggregate gradation plays vital role in the rutting behavior; different gradation yield different strength and durability of pavement structures. This report presents mix design and creep performance data of four gradations; gap graded, continuous graded, open graded and dense graded. The aggregates used are crushed granite (coarse aggregate), river sand (fine aggregate) and ordinary Portland cement (OPC) as filler, while the bitumen used is 80 penetration bitumen. The evaluation of creep performance is done using the Dynamic Creep Test, and the result showsthat dense graded mixture yields the best creep resistance

Comparison on the Mechanical Properties of Wearing Course Materials between JKR & LLM Specification

It is common knowledge that instability and unreliability are the two most common types of damages that can be sustained by a road's pavement. These are primarily the result of an increase in the number of vehicles, particularly those with high axle loads, as well as the effects of the surrounding environment, as well as mistakes made during construction and design. The design of flexible pavement takes into account the axle load limits as well as the weather conditions

The Correlation between Compaction Degree and Performance Life of Asphalt Concrete

Inadequate compaction of wearing course of asphalt concrete is a common phenomenon in road construction. Contractors choose to apply a minimum compaction effort in order to cut costs and speed up construction process. Even though the requirement set by relevant authorities such as, Jabatan Kerja Raya (JKR), most of the end product failed to achieve this requirement. Inadequate compaction results in pavement with reduced rutting and fatigue life. This study aims to establish a correlation between compaction degree and performance life of asphalt concrete. Such correlations will provide awareness to the practitioner that the void content is a crucial factor in the performance life of asphalt concrete. Three types of tests were carried out to provide quantitative information on performance life of asphalt concrete at various degrees of compaction. The tests were dynamic creep test, fatigue test and wheel tracking test. The mix type is wearing course and the mix designation is asphalt concrete wearing course or ACW20. The material includes asphalt cement, aggregate and cement as tiller. Based on JKR recommendation, penetration graded asphalts were used. The sieve analysis was performed according to JKR specifications. From dynamic creep test, the correlation between compaction degree and rutting life obtained was Y,%. = 4. x 10-145X 7767`('l ow orosit YA 10 X 1217 (medium porosity) and YA = (3 x 10"t') X, 13308(h igh porosity). where Y,, as rutting life in rasa and XA as compaction degree in percentage. Low porosity specimen is less susceptibility to rut depth than the high porosity specimen. The correlation between porosity and rate of wheel tracking obtained in this study was Yn = 0.0018 Xa 18 624w ith R` =0.7138, where Yß is rate of wheel tracking in mm/min and XE4 is porosity. This correlation emphasizes that low porosity specimen is more resistant to permanent deformation than high porosity specimen. For fatigue failure, the same trend can be concluded

Recycled asphalt mixtures produced with high percentage of different waste materials

The use of sustainable solutions in construction is not just an option, but is increasingly becoming a need of the Society. Thus, nowadays the recycling of waste materials is a growing technology that needs to be continuously improved, namely by researching new solutions for waste valorisation and by increasing the amount of wastes reused. In the paving industry, the reuse of reclaimed asphalt (RA) is becoming common practice, but needs further research work. Thus, this study aims to increase the incorporation of RA and other waste materials in the production of recycled asphalt mixtures in order to improve their mechanical, environmental and economic performance. Recycled mixtures with 50% RA were analysed in this study, including: i) RA selection, preparation and characterization; ii) incorporation of other waste materials as binder additives or modifiers, like used motor oil (UMO) and waste high density polyethylene (HDPE); iii) production of different mixtures (without additives; with UMO; with UMO and HDPE) and comparison of their performance in order to assess the main advantages of each solution. With this study it was concluded that up to 7.5 % of UMO and 4.0 % of HDPE can be used in a new modified binder for asphalt mixtures with 50 % of RA, which have excellent properties concerning the rutting with WTS = 0.02 mm/103 cycles, the fatigue resistance with ε6 = 160.4, and water sensitivity with an ITSR of 81.9 %.The authors would like to acknowledge the financial and material support given by some institutions. In fact, this work was funded by FEDER funds through the Operational Competitiveness Program – COMPETE and by National funds by FCT – Portuguese Foundation for Science and Technology in the scope of Project FCOMP-01-0124-FEDER-020335 (PTDC/ECM/119179/2010) and the Project SI Innovation 7603, as well as the FCT PhD grant SFRH/BD/85448/2012. Thanks are also due to the Companies Gintegral (for the supply of recycled HDPE) and CEPSA (for the supply of bitumen)

表層用アスファルト混合物の力学特性に骨材粒度が及ぼす影響の包括的評価

国立大学法人長岡技術科学大

Alternative Fillers in Asphalt Concrete Mixtures: Laboratory Investigation and Machine Learning Modeling towards Mechanical Performance Prediction

In recent years, due to the reduction in available natural resources, the attention of many researchers has been focused on the reuse of recycled materials and industrial waste in common engineering applications. This paper discusses the feasibility of using seven different materials as alternative fillers instead of ordinary Portland cement (OPC) in road pavement base layers: namely rice husk ash (RHA), brick dust (BD), marble dust (MD), stone dust (SD), fly ash (FA), limestone dust (LD), and silica fume (SF). To exclusively evaluate the effect that selected fillers had on the mechanical performance of asphalt mixtures, we carried out Marshall, indirect tensile strength, moisture susceptibility, and Cantabro abrasion loss tests on specimens in which only the filler type and its percentage varied while keeping constant all the remaining design parameters. Experimental findings showed that all mixtures, except those prepared with 4% RHA or MD, met the requirements of Indian standards with respect to air voids, Marshall stability and quotient. LD and SF mixtures provided slightly better mechanical strength and durability than OPC ones, proving they can be successfully recycled as filler in asphalt mixtures. Furthermore, a Machine Learning methodology based on laboratory results was developed. A decision tree Categorical Boosting approach allowed the main mechanical properties of the investigated mixtures to be predicted on the basis of the main compositional variables, with a mean Pearson correlation and a mean coefficient of determination equal to 0.9724 and 0.9374, respectively

Image Based Modeling Technique for Pavement Distress surveys: a Specific Application to Rutting

Image-based modeling (IBM) is a well-known technique to obtain high quality 3D models based on multi view images. IBM started being used in several applications such as inspection, identification of objects and visualization, due to the user-friendly approach, the low cost and highly automated technique. This paper focuses on the investigation of the potential application of IBM in the diagnosis of road pavement distresses and in particular rutting. Indeed, the evaluation of the rutting distress is a fundamental step to define the whole state of a pavement as demonstrated by the calculation of Present Serviceability Index (PSI). Currently, the permanent deformation is measured monitoring visually the rut depth with the approximations that this procedure involves. Nevertheless, the exact measure of the rut depth is necessary to evaluate precisely the cause and the severity of this distress and be effective in the maintenance and rehabilitation of the pavement structure. The objective of this study is to apply the IBM technique on a laboratory rutted sample, in order to verify the accuracy of the method in determining the rut depth. To achieve this, a comparison has been made between the 3D model obtained with IBM and the one obtained with blue led 3D scan (Artec Spider) of the same rutted asphalt concrete. The metric accuracy of the model is then defined and its validity is assessed, in terms of distress diagnosis

Viability of using high amounts of steel slag aggregates to improve the circularity and performance of asphalt mixtures

Steel slag is a byproduct generated as waste during the steelmaking process and can be considered a cost‐effective and environmentally acceptable alternative to replace natural aggre-gates. Using steel slag aggregates (SSA) to produce asphalt mixtures promotes sustainability and circular economy principles by using an industrial byproduct as a raw material. Thus, this work mainly aims to design more sustainable asphalt mixtures with high amounts of SSA that fit the circular economy expectations. This work developed two asphalt mixtures with SSA for surface (AC 14 surf) and binder/base (AC 20 bin/base) courses. Initially, the excellent wearing and polishing resistance of SSA and their good affinity with bitumen demonstrated the potential of this byproduct to be used in asphalt mixtures. Then, when analyzing the influence of using two different SSA incorporation rates (50% and a percentage close to 100%) in both asphalt mixtures, it was concluded that the use of SSA should be limited to 75% to avoid excessive air void contents and durability problems. The importance of considering the different particle densities of SSA and natural aggregates was highlighted during the mix design by defining a relationship between an effective and equivalent binder content. Finally, the mechanical performance of AC 14 and AC 20 with 75% SSA incorporation was compared to identical conventional mixtures produced with natural granite ag-gregates. The results obtained showed that the asphalt mixtures with 75% SSA have some worka-bility problems due to the rough and porous surface of SSA. However, they present an excellent water sensitivity and permanent deformation resistance, surpassing the performance of the conventional asphalt mixtures.This research was funded by the PORTUGAL 2020 Partnership Agreement through the Competitiveness and Internationalization Operational Program (POCI) and the European Regional Development Fund (ERDF), under the R&D Project “RENEw—Construction waste for a circular economy”, with reference POCI-01-0247-FEDER-033834