Composition of abraded dust from asphalt pavement produced using ferrochromium smelter slag (OKTO-aggregate)

This report describes an investigation that took place at Aalto University commissioned by the Finnish Transport Agency about asphalt dust containing OKTO-aggregate. In the fall of 2013, Finnish newspaper headlines began to raise the issue of the occurrence of damaged timing belts in the Oulu region. It seemed to only concern certain models and was found in the form of a dust. The press reasoned that this "mysterious" dust must have originated from the aggregates abraded from the local Oulu roads. More specifically, it was attributed to the OKTO-aggregate used in surface wearing course mixtures on high traffic volume roads. The OKTO-aggregate (OKTO-murske in Finnish) is a brand name for the man-made byproduct of the smelter slag from the Outokumpu Tornio ferrochromium plant. Natural rock aggregates are substituted by this material in high volume roads due to its excellent abrasion resistance against studded tire wear. The conclusion is that the possible contribution of OKTO-aggregate to the mechanical breakage or abrasion of car parts was considered insignificant compared with the other fragments, such as corundum, that were also detected in the car dust. Furthermore, OKTO-aggregate was found to be much less reactive with deicing salts than the rock aggregate used in the Oulu region. Therefore, the OKTO-aggregate does not significantly contribute to the chemical corrosion of car parts

Durability of Ring-Road II asphalt pavement - Phase I report on forensic analysis of Ring-Road II pavement distresses

This report presents findings from prematurely failed pavement of Ring-Road II (Kehä II) in Espoo, Finland. The road had excessive potholes, cracking, raveling and stripping only five years after construction. Core samples taken for this study revealed also that pavement layers were partially separated due to the lack of bonding. Research focus was to determine the causes of Stone Mastic Asphalt surface layer failure. Documentation of mix design, construction and material quality analysis, prior to and after construction, was compared to the samples collected from the road. Traditional quality assessment of the pavement by means of binder content and aggregate gradation analysis, air voids content, Indirect Tensile Strength and Stiffness, as well as binder tests including Penetration, Ring and Ball Softening Point and rheological characterization by Dynamic Shear Rheometer (DSR) were performed. Discrepancy was found in filler composition and additional analysis was made by applying standard analytical procedure of hydrochloric acid solubility. The findings were confirmed by means of Thermogravimetral Analysis (TGA), X-Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM), supported by BET-adsorption surface area measurements. The investigation revealed presence of fly ash that was apparently used for extending limestone filler during construction. It can be concluded that the main reason for the pavement failure was due to this substitution and the consequent problems that followed in the construction and thereafter in the pavement performance

The physicochemical influence of the inorganic phase on the aging and performance of asphalt pavements in Finland

The need to understand the reasons behind the deterioration of asphalt pavements led to the research focused on the relationship between molecular interactions within this composite material and its macroscopic properties. The aim of the work was to establish the risks arising from the interaction between bitumen and the inorganic compounds, namely fine particles passing the 125 μm sieve. The first case study, the forensic analysis of failed asphalt pavement, Ring Road II in the Helsinki Metropolitan Area, revealed that a substitution of the asphalt concrete component occurred between the mix design and production, mass by mass. The mineral filler used contained fly ash in lieu of using pure limestone as was designed. This work investigated how physicochemical properties, such as the altered density and chemical composition of the filler, affect the properties of asphalt during recycling in Finland. The iron compounds located on the surface of the filler grains, in addition to the differences in the volume of the reinforcing phase, correlated well with the increase in the softening point of asphalt mastic. Additionally, the interaction of iron rich fillers with deicing chemicals resulted in higher chloride accumulation in the inorganic fines of asphalt concrete during service life. During the recycling of asphalt concrete, the accumulation of chlorides could prove dangerous, if those inorganic compounds catalyzed the bitumen oxidation. The in-situ laboratory study of the oxidation reaction of bitumen demonstrated how the presence of inorganic salts alters the mechanism of reaction. The iron (III) chloride was confirmed as a catalyst of oxidation, while a typical deicing chemical, calcium chloride, left the reaction mechanism and its rate unaltered. What is more important, the novel time-resolved infrared spectroscopy analysis provided insight into pure bitumen oxidation as well, revealing that the reaction at high temperatures occurs step-wise i.e., thiol oxidation followed by ketone formation. Controlling the reaction by blocking the thiol oxidation via interaction with copper successfully hindered the ketone formation. The novel approach to asphalt concrete engineering on a molecular level is promising, but the effect of such control on the physical properties of asphalt pavements still needs to be confirmed. The effect which oxidation of bitumen, followed by blending with fresh organic material, has on the molecular weight distribution, change in polarity, and rheological characteristic was studied in laboratory conditions to simulate four cycles of reuse. Increasing molecular weight distribution correlated well with an increase in the elastic response of the material. The loss of the ability to dissipate energy by flowing was postulated to cause the declining performance in the cold climate regions

The research on the hot in-place recycling of asphalt pavements by the REMIX technique

The aim of the research program was to improve the efficiency of the paved road maintenance by providing new information on their life-cycle management. The emphasis of the research was to extend the life cycle of the road pavements and to focus on improving the long-term durability of AC and SMA mixtures and the controlled increase in their reuse by using REMIX technology. As a result of the research, new know-how emerged, which means that the long-term durability of road pavements can be improved and recycling increased. From the road agency's point of view, this is achieved by reforming instructions and quality control requirements, while from the point of view of the contractor, by providing new knowledge to manage materials and improve design practices and working methods. New research methods and their application were developed in the study. For the bitumen testing, the dynamic shear rheomether (DSR) and the infrared spectrometer (FT-IR) were utilized in addition to the conventional testing methods to improve the quality control of bitumen testing required for the reuse. The result of the study transferable into the industry is a methodology for estimating the amount of materials needed for the recovery of aged bitumen from the REMIX treated road surface by selecting a clear rheological goal for the outcome of the work. A procedure was developed to conduct the necessary calculations aiming at a certain rheological target in line with an acceptable performance. By means of the detailed procedure, the new raw materials and their ratios such as rejuvenators are selected in such a way that in the reuse the bitumen rheological properties are at least maintained. This will improve the life-cycle efficiency of asphalt pavement maintenance.Tutkimusohjelman tavoitteena oli tehostaa päällystettyjen maanteiden ylläpidon taloudellisuutta tuottamalla uutta tietoa niiden elinkaaren hallintaan. Tutkimuksen keskiössä on maantiepäällysteiden elinkaaren pidentäminen ja päähuomio on AB- ja SMA –päällysteiden pitkäaikaiskestävyyden parantamisessa ja niiden uusiokäytön hallitussa lisäämisessä REMIX-tekniikalla. Tutkimuksen tuloksena syntyi uutta osaamista, jonka pohjalta maantiepäällysteiden pitkäaikaiskestävyyttä pystytään parantamaan ja uusiokäyttöä lisäämään. Tilaajan näkökulmasta tähän päästään ohjeita ja laatuvaatimuksia uudistamalla. Urakoitsijan näkökulmasta uutta osaamista tarvitaan materiaalien, suunnittelukäytännön ja työmenetelmän hallintaan. Tutkimuksessa kehitettiin uusia tutkimusmenetelmiä ja niiden käyttöä. Uusina laitteina bitumin testauksessa käytettiin dynaamista leikkausreometria (DSR) ja infrapuna spektrometriaan perustuvaa analytiikkaa (FT-IR), joiden avulla voidaan myös parantaa uusiokäytössä tarvittavan bitumitestauksen laadunvalvontaa. Tutkimuksen keskeinen tulos on menetelmä, jolla voidaan arvioida tiellä vanhentuneen bitumin elvytystä REM-pintauksessa siten että valitaan selkeä reologinen tavoite työn lopputulokselle, tehdään tarvittavat laskelmat ja verrataan saatua lopputulosta asetettuun tavoitteeseen. Menetelmän avulla valitaan raaka-aineet ja niiden seossuhteet niin, että uusiokäytössä bitumin reologiset ominaisuudet pyritään vähintäänkin säilyttämään. Tämä parantaa päällysteiden ylläpidon elinkaaritehokkuutta

The Bitumen Related Problems Observed on Soft Asphalt Concrete Pavements : Case Study

Publisher Copyright: © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Four roads paved with soft asphalt concrete during the autumn of 2017 by one contractor in a Nordic country, damaged during the following winter. The road users reported that bitumen detached from the surface and was sticking to the fur of pet animals, as well as to the surfaces of the vehicles. The article discusses aspects connected with production and paving, which may have affected the performance. In addition, the material analysis of the samples collected from the field was performed. The core samples were tested by Indirect Tensile Strength (ITS). Because of the low strength of the soft asphalt concrete the ITS is not routinely performed for this material. Therefore, the results of ITS were inconclusive due to the lack of reliable references. The gradation was analyzed after the bitumen extraction and recovery, and no abnormalities were discovered. The Zero Shear Viscosity at multiple temperatures and fractional composition was performed on both extracted and reference binders type V1500 and 650/900 (EN 12591) after evaluation of bitumen purity with infrared spectroscopy. The bitumen extracted from the most questionable pavement expressed comparable rheological behavior to references, but was characterized by the exceptionally high content of saturates. The short research project was unable to determine if the damage was a result or the reason for the altered binder composition. Nevertheless, the link between abnormal performance observed in the field and abnormal chemical characteristic of bitumen is reported.Peer reviewe

The research on the hot in-place recycling of asphalt pavements by the REMIX technique

The aim of the research program was to improve the efficiency of the paved road maintenance by providing new information on their life-cycle management. The emphasis of the research was to extend the life cycle of the road pavements and to focus on improving the long-term durability of AC and SMA mixtures and the controlled increase in their reuse by using REMIX technology. As a result of the research, new know-how emerged, which means that the long-term durability of road pavements can be improved and recycling increased. From the road agency's point of view, this is achieved by reforming instructions and quality control requirements, while from the point of view of the contractor, by providing new knowledge to manage materials and improve design practices and working methods. New research methods and their application were developed in the study. For the bitumen testing, the dynamic shear rheomether (DSR) and the infrared spectrometer (FT-IR) were utilized in addition to the conventional testing methods to improve the quality control of bitumen testing required for the reuse. The result of the study transferable into the industry is a methodology for estimating the amount of materials needed for the recovery of aged bitumen from the REMIX treated road surface by selecting a clear rheological goal for the outcome of the work. A procedure was developed to conduct the necessary calculations aiming at a certain rheological target in line with an acceptable performance. By means of the detailed procedure, the new raw materials and their ratios such as rejuvenators are selected in such a way that in the reuse the bitumen rheological properties are at least maintained. This will improve the life-cycle efficiency of asphalt pavement maintenance.Tutkimusohjelman tavoitteena oli tehostaa päällystettyjen maanteiden ylläpidon taloudellisuutta tuottamalla uutta tietoa niiden elinkaaren hallintaan. Tutkimuksen keskiössä on maantiepäällysteiden elinkaaren pidentäminen ja päähuomio on AB- ja SMA –päällysteiden pitkäaikaiskestävyyden parantamisessa ja niiden uusiokäytön hallitussa lisäämisessä REMIX-tekniikalla. Tutkimuksen tuloksena syntyi uutta osaamista, jonka pohjalta maantiepäällysteiden pitkäaikaiskestävyyttä pystytään parantamaan ja uusiokäyttöä lisäämään. Tilaajan näkökulmasta tähän päästään ohjeita ja laatuvaatimuksia uudistamalla. Urakoitsijan näkökulmasta uutta osaamista tarvitaan materiaalien, suunnittelukäytännön ja työmenetelmän hallintaan. Tutkimuksessa kehitettiin uusia tutkimusmenetelmiä ja niiden käyttöä. Uusina laitteina bitumin testauksessa käytettiin dynaamista leikkausreometria (DSR) ja infrapuna spektrometriaan perustuvaa analytiikkaa (FT-IR), joiden avulla voidaan myös parantaa uusiokäytössä tarvittavan bitumitestauksen laadunvalvontaa. Tutkimuksen keskeinen tulos on menetelmä, jolla voidaan arvioida tiellä vanhentuneen bitumin elvytystä REM-pintauksessa siten että valitaan selkeä reologinen tavoite työn lopputulokselle, tehdään tarvittavat laskelmat ja verrataan saatua lopputulosta asetettuun tavoitteeseen. Menetelmän avulla valitaan raaka-aineet ja niiden seossuhteet niin, että uusiokäytössä bitumin reologiset ominaisuudet pyritään vähintäänkin säilyttämään. Tämä parantaa päällysteiden ylläpidon elinkaaritehokkuutta

Thin layer chromatography performed in stages to identify the presence of aromatic like fraction in chosen bitumen modifiers

The organic modifiers are used to alter the rheology of the binder in the asphalt concrete at an added cost. For quality control purpose, recognizing if such material is present in the final blend is of an interest. The thin layer chromatography (TLC) using a flame photometric detector (FPD), in addition to the typical flame ionization detector, was demonstrated hereby as a potential analytical tool for this problem, differentiating between tall crude oil based anti-aging agent, polymer, oxidized bitumen and gilsonite. Gilsonite and anti-aging agent consists of the material soluble in solvent used in the development of the fraction referred to as aromatics. Due to the hindered mobility of modifier molecules on the stationary phase, the elution of aromatic fraction stops at position convoluted with polars I and polars II fraction regions, colloquially referred to as resins and asphaltenes. However, for the color of this fraction within gilsonite is different. The presence of gilsonite is thus identifiable visually after the second development bath, but also to an extent with FPD from the final chromatogram. The thin layer chromatography-flame ionization detectors (TLC-FID) procedure is suggested to be supplemented by infrared spectroscopy to discriminate between non-bituminous and bituminous modifiers of similar response during fractionation. (C) 2020 Periodical Offices of Chang'an University. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd.Peer reviewe