Thermal suspectability analysis of the reuse of fly ash from cellulose industry as contribution filler in bituminous mixtures

The increased population has accelerated pavement deterioration of and boosted production of residues, generating a constant environmental problem. One of the main problems of pavements is a failure to develop union between bituminous mastic ligand and aggregate. The following study evaluates the use of ash from cellulose incineration as a contribution filler to improve thermal susceptibility of pavements in different climatic zones. The applied methodology for dosage was based on volumetric criteria and state curves. The obtained results showed that reusing this residue in determined conditions (Cv/Cs???1) offers lower wear loss to 35% of temperatures between ?10 and 60?°C, due to the Cv/Cs?=?0.75 ratio that maximizes the cohesive properties of the mixture. Therefore, we showed that this type of industry residue can be reused without complication in zones of certain climatic criteria and that it provides improved properties to the asphalt mix compared to conventional mixes

Effect of copper slag addition on mechanical behaviour of asphalt mixes containing reclaimed asphalt pavement

Annually, copper production and refining processes of generate large volumes of copper slag, and the disposal of this waste remains a major economic and environmental problem. This annual production causes an increase in the number and volume of landfills, as well as the quantity of slag that backs up landfills, it also produces leachates which contain metals such as Cu, Pb, Hg and SO2. In this research, friction and cohesive qualities of copper slag are exploited, in order to incorporate this slag as aggregate in asphalt mixes containing Reclaimed Asphalt Pavement (RAP). Results demonstrate that the use of copper slag in an addition percentage of 35% is favorable, because flow values increase and stability values decrease. The Marshall Quotient is reduced up to 27%, improving the performance of mixes with RAP and obtaining behavior similar to a traditional mixture. This improvement is also reflected in an 8% increase in the indirect tensile strength, which stands the use of copper slag as a solution in RAP applications with more demanding tensile and fatigue requirements.The presented results are part of the FONDECYT Initiation into Research project No. 11140889, funded by CONICYT-Chile, and the DID S-2014-27 project, funded by the Universidad Austral de Chile. The authors also would like to thank Bitumix S.A. and its CDI, CONAV S.A. and the Regional Laboratory of Transportation of Puerto Montt for the material donations and facilitation of their dependencie

Use of plastic scrap in asphalt mixtures added by dry method as a partial substitute for bitumen

In recent decades, the generation of plastic waste has increased substantially worldwide, with the result that more of such waste is introduced into the environment. Currently, most polymers (polyethylene terephthalate, polyethylene, polyvinyl chloride, and others) are recycled. However, some are rejected for recycling in the primary separation processes due to their physical condition, contamination, or size. These materials are called plastic scrap. In this research, the use of plastic scrap added by dry method was evaluated as a replacement for bitumen in asphalt mixtures. Two sizes of plastic scrap, coarse and fine, were considered. An AC16S semi-dense mixture was designed for this purpose, with a 10% reduction in binder, and 10% and 20% of plastic scrap binder was added in coarse and fine sizes. The results obtained in the Marshall stability and flow test showed reduced moisture damage, greater indirect tensile strength, higher air void content, and a 2% decrease in the conserved tensile strength ratio while the same usage field as the conventional mixture was maintained. Meanwhile, significant decreases in plastic deformations, as compared to traditional values, were obtained from resilient modulus and rutting tests

The use of copper slags as an aggregate replacement in asphalt mixes with RAP: Physical-chemical and mechanical behavioural analysis

Copper slag (CS) is a derivative of copper production that is mainly composed of heavy metals. The large amount of this material accumulated around the world entails a serious environmental danger. Its use as a replacement of mineral aggregate in asphalt mixtures would allow to increase the durability and resistance, taking advantage of its physical-chemical properties. In this research, physicochemical analyses of different combinations of CS, reclaimed asphalt pavements (RAP), asphalt cement and aggregates by X-Ray Diffraction (XRD) and Fourier-Transform InfraRed spectroscopy (FT-IR) were developed. Subsequently, Marshall stiffness ratio, indirect tensile strength (IDT) and resilient modulus tests were performed to determine their implication in mechanical behaviour. Asphalt mixes with ranges from 45 to 55% of recycled material have improved stability, Marshall Flow and Stiffness ratio, obtaining values comparable with those from a conventional mixture. At the same time, its resilient modulus and IDT values increased by 35% compared to conventional mixes. To maintain values similar to conventional mixes, when the amount of RAP decreases the amount of CS should be increased, with a maximum value of 35%. This behaviour is explained by the presence of fayalite and magnetite in CS, which are hard, dense and hydrophobic components that produce increased elastic deformation of the binder before breaking.These results are part of a project funded by: the Universidad Austral de Chile [DID S-2014-27]; and a CONICYT-Chile project [FONDECYT Initiation into Research No. 11140889]

Reduction in the use of mineral aggregate by recycling cellulose ashes to decrease the aging of hot asphalt mixtures

The rapid development that our society is experiencing effects road management, therefore developing economical and efficient solutions, as well as extending road service life is indispensable. Aging is a problem associated to the majority of failures at the pavement surface layer (cracks, fissures, fatigue), including those produced by traffic solicitations. Diverse studies indicate that alterations to mixtures due to age can be decreased by incorporating a filler or mineral filler. Therefore, the present study incorporates cellulose ashes at different Cv/Cs concentrations as contribution filler in bituminous mastic, analysing its influence on aging resistance using the Cantabro wear test. The results indicated that using cellulose ash as contribution filler allows promising results to be obtained in regards to aging resistance of asphalt mixtures, if they are incorporated in concentrations close to or equal to the critical concentration, with an increase in aging resistance from 45.3 to 48.6% depending on the type of bitumen used. Therefore, incorporating them into the design of asphalt mixtures could be an efficient and economical solution to the current problems of early cracking and pavements with a service life lower than the estimated, although a more thorough analysis of its behaviour in other tests and service conditions is required in bituminous mixtures.The presented results are part of the FONDECYT Initiation 2013 into Research project No. 11130309, funded by CONICYTChile. The authors also would like to thank ARAUCO, Bitumix S.A. and Química Latinoamericana for the material donations

Development of an estimative model for the optimal tack coat dosage based on aggregate gradation of hot mix asphalt pavements

In this work the performance of tack coats on asphalt pavement layers is analysed. Adjustment models based on experimental measurements were implemented, relating surface layer macro-texture and aggregate content larger than 8 mm. The best fits were obtained with a Gompertz model, which follows the expected physical macro-texture changes outside the test range. Shear strength was analysed, through prediction curves of each evaluated tack coat dosage, with an optimum tack coat performance for aggregate contents larger than 8 mm between 45% and 50%, and no relevant influence of the tack coat dosage used.The authors would like to acknowledge the support provided by the Technologic Research Construction Group (GITECO) and the Group of Roads of Santander at Cantabria University for the development of tests and samples. We would also like to thank the company Emilio Bolado S.L. and the Society for the Development of Cantabria Region (SODERCAN) for the material provided, and the DID Research Department from the Austral University of Chile for the support

Study of the mechanical behavior of asphalt mixtures using fractional rheology to model their viscoelasticity

This study focuses on the mechanical behavior of asphalt mixtures composed of aggregate particles attached with an asphalt binder. Asphalt mixtures are viscoelastic composite materials widely used in the construction of pavement layers. The modelling of such materials is currently done using the Burgers model. However, this model is limited when explaining some of the viscoelastic phenomena of an asphalt mixture, mainly because the Burgers model was developed for a single material with a dual nature. This work presents a new approach that provides a more appropriate framework for studying asphalt mixtures. The model assumes an aggregate particle enclosed by an asphalt material. Viscoelastic equations were developed using derivatives of fractional order. Then, the creep, recovery, and relaxation phenomena in an asphalt mixture were analyzed using the new model. Unlike the Burgers model, the new model can predict the elastic jump observed at the beginning of the creep modulus. Thus, the new model seems to describe better those practical cases of asphalt mixtures used in the construction of pavement layers. The new model can be used to modify the properties of the binder for designing optimized and more resistant asphalt mixtures

Test methods and influential factors for analysis of bonding between bituminous pavement layers

The durability and maintenance of pavements depend on several factors. One of the most influential is the bond between layers. This bond is responsible for ensuring all layers behave as a single entity, reducing cracks and deformation of the pavement. Several methods, developed by different authors over the past 30 years, to measure bonding between layers are analyzed in this paper. Different research lines are discussed, concluding that the most influential variables are: tack coat type, dosage, mixture type, surface characteristics, temperature, and emulsion breaking time. In order to reach the highest bond strength values, the following factors should be considered: high values of surface macro-texture, low temperatures, the use of heat-adhesive emulsion, a dosage from 300 to 450 g/m2 of residual bitumen and the compaction after emulsion break. Moreover, a non-destructive test method to assess tack coat dosage on site is proposed

Rheological analyses of binders modified with triple combinations of Crumb-Rubber, Sasobit and Styrene-Butadiene-Styrene

The development of polymer-modified asphalt (PMA) has been a widely used technique by many researchers. Moreover, further modification of PMA binders has generated interest due to possible improvements in performance and cost. In this regard, Sasobit wax has been an alternative to reduce costs in Crumb-Rubber (CR) and Styrene-Butadiene-Styrene Copolymer (SBS) binders. However, there is little detail on the rheological behaviour of CR-SBS-Sasobit triple-modified samples for failure and damage resistance properties. Therefore, this study shows various properties of binders with triple modification of CR-SBS-Sasobit at different dosages. For this purpose, the development of single, double and triple modifications has been proposed to be tested by Multiple Stress Creep Recovery (MSCR) for permanent deformation. In the case of radial cracking and thermal cracking, it is evaluated by linear amplitude sweep test (LAS) and binder creep energy test (BYET). The results indicate that a CR-SBS combination in single or double addition achieves good thermal stability and behaviour. However, a higher elasticity is achieved in the case of a triple modification with CR-SBS-Sasobit. Specifically, Sasobit achieves 67% and 28% reduction in the cumulative deformation of MSCR for a variation of 40–80 °C, respectively. Concerning fatigue life (Nf), it is shown that CR-SBS modifications do not always acquire higher Nf than single modifications. However, adding Sasobit in triple modifications increases these values, generating bitumen with higher strength. It is also shown that adding Sasobit is a viable modifier in yield, even increasing the yield energy (Er) for samples with equal CR-SBS and reducing the percentage of SBS in the sample

Study of the permanent deformation of binders and asphalt mixtures using rheological models of fractional viscoelasticity

ABSTRACT: The accumulation of load on asphalt pavement as a result of increased vehicle traffic generates problems in the asphalt layer due to permanent deformation. For correct design, it is essential to carry out a rheological characterization of the aggregate-binder materials that make up the asphalt mix. This article shows the analysis of permanent deformation based on the rheological behavior of asphalt mixtures and binders. Experimental tests based on creep and recovery phenomena allow the study of permanent deformations using theoretical models of fractional viscoelasticity. The rheological characterization allows us to detail the elasticity of the aggregate, ξ2, and the elastic-viscous properties of the different binders used, ξ1 and η .The results obtained show that it is possible to predict the deformations of the recovery phenomenon in asphalt mixtures from the rheological values (aggregate-binder) obtained in the creep process. Besides, the properties of the asphalt binder (ξ1 and η) correlate with the recovery phenomenon of the MSCR test for conventional and modified materials. The methodology proposed allows a better understanding of the states of permanent deformation to improve the design of binders and asphalt mixtures..The authors gratefully acknowledge the institutional support provided by the Department of R+D of the University Austral of Chile (DID UACh) and to the Santander Bank Iberoamerican Scholarship Program, which made it possible to carry out this research. The authors would also like to thank the GITECO and GCS research groups from the University of Cantabria (Spain) for their support