Bewertung der Einflussgrößen auf die thermisch-oxidative Alterung von Bitumen im Asphalt

Product Description

Summary The decisive properties of the binder bitumen for use in asphalt road construction are characterized by cohesion, adhesion and aging. Cohesion describes the internal binding forces of the material and adhesion the bonding to the aggregates. The aging of bitumen refers to the change in the chemical, physical and rheological properties of the binder over the service life. This irreversible process begins already during production and ultimately leads to a change in the material properties of the building material "asphalt". The aging process of asphalt is determined by a multitude of influencing factors and can lead to premature damage under unfavorable boundary conditions. Therefore, knowledge of the decisive influencing factors on aging and quantification, as a prerequisite for durable asphalt pavements, is of particular interest. In numerous research works, selected influencing factors have already been investigated on different asphalts. It could be demonstrated that the binder film thickness, the void content as well as the binder and aggregate type have a decisive influence on the aging behavior. A targeted investigation for quantifying the influencing factors through variation of the mixture composition and aging boundary conditions has not been carried out so far. Within the framework of this work, the mixture composition was varied on selected aggregate and binder types in order to quantify the influencing factors. For this purpose, an open-porous (PA 11) as well as a dense asphalt (AC 11) with two road construction binders (20/30 and 70/100) in combination with three different aggregate types were aged in time-lapse under laboratory conditions using an asphalt aging procedure. Furthermore, within the framework of the investigations, a new procedure for measuring the "average mastic film thickness" was developed. The investigation results have shown that a small change in the mixture composition leads to differently proceeding aging processes. With porous aggregates, an accelerated aging and when using calcium hydroxide filler, a slower proceeding asphalt aging could be quantified. The influence of the initial stiffness of the used binder as well as the influence of binder amount, binder film thickness, mastic film thickness and void content could also be described with mathematical approaches. Additionally, estimation functions for predicting aging behavior were established, which provide a basis for further research activities. Abstract The relevant properties of bituminous binders for the usage in asphalt are cohesion, adhesion and ageing. The cohesion describes the inner bonding forces and the adhesion the binding strength of the material with the aggregates. Ageing characterizes the changing of chemical-, physical- and rheological properties of the binder which is caused of the external influence factors by using in the asphalt. This irreversible ageing process starts already by the production and leads finally to a change of the material properties of the construction material "asphalt". The ageing process of asphalt is affected by a multiplicity of influence factors and can effect an early damaging of the pavement by rapid ageing. Therefore the knowledge of the relevant influence factors is for a durable dimensioning of asphalt pavements a matter of particular interest. Many research studies in the past already analyzed selected influence factors on different asphalt mixtures. Thereby the influence of binder film thickness, voids in the asphalt as soon as the sort of binder and aggregates were determined. A selective analysis of multitude influence factors with identical binder and aggregate sorts by variation of the mixture composition and ageing conditions was not conducted by now. Within this dissertation selected aggregate and binder sorts were used to get mixture variations for quantifying the influence factors. For that purpose porous asphalt (PA 11) and asphalt concrete (AC 11) mixtures in combination with three sorts of aggregates (Diabase, Quartz Porphyry and hydrated Limestone Filler) and two binders (20/30 and 70/100) were chosen for the ageing under laboratory conditions with a new kind of asphalt ageing method. Also a new method for determination of the mastic film thickness of asphalt mixtures was developed. One of the findings of the analysis was that even minor changes in mixture different ageing procedures. An accelerated ageing process with porous aggregates was shown while the usage of hydrated limestone filler affected a delay of the ageing process. Also the influence of the initial stiffness of the binder sort as well as the influence of binder film thickness, binder ratio, mastic film thickness and air void ratio on the ageing was quantified. Additionally estimating functions for the prognosis of the ageing behavior were given. Abstract The relevant properties of the binder bitumen for use in asphalt road construction are characterized by cohesion, adhesion and aging. Cohesion describes the internal bonding forces of the material and adhesion the binding to the aggregates. The aging of bitumen refers to the change in the chemical, physical and rheological properties of the binder during its service life. This irreversible process begins already during production and ultimately leads to a change in the material properties of the building material "asphalt". The aging process of asphalt is determined by a multitude of influencing factors and can lead to premature damage under unfavorable conditions. Therefore, knowledge of the relevant influencing factors on aging and quantification, as a prerequisite for durable asphalt pavements, is of particular interest. In numerous research works, selected influencing factors on different asphalts have already been investigated. It could be proven that the binder film thickness, the void content as well as the binder and aggregate type have a decisive influence on the aging behavior. A targeted investigation for quantifying the influencing factors by varying the mixture composition and aging conditions has not been carried out so far. Within the framework of this work, the mixture composition was varied on selected aggregate and binder types in order to quantify the influencing factors. For this purpose, an open-porous (PA 11) as well as a dense asphalt (AC 11) with two road construction binders (20/30 and 70/100) in combination with three different aggregate types were aged in a time-lapse manner under laboratory conditions using an asphalt aging method. Furthermore, within the framework of the investigations, a new method for measuring the "average mastic film thickness" was developed. The investigation results have shown that a small change in the mixture composition leads to differently proceeding aging processes. For porous aggregates, an accelerated aging and for the use of calcium hydroxide filler, a slower proceeding asphalt aging could be quantified. The influence of the initial stiffness of the binder used as well as the influence of binder content, binder film thickness, mastic film thickness and void content could also be described with mathematical approaches. Additionally, estimation functions for predicting aging behavior were established, which provide a basis for further research activities. Abstract The relevant properties of bituminous binders for the usage in asphalt are cohesion, adhesion and ageing. The cohesion describes the inner bonding forces and the adhesion the binding strength of the material with the aggregates. Ageing characterizes the changing of chemical-, physical- and rheological properties of the binder which is caused of the external influence factors by using in the asphalt. This irreversible ageing process starts already by the production and leads finally to a change of the material properties of the construction material "asphalt". The ageing process of asphalt is affected by a multiplicity of influence factors and can effect an early damaging of the pavement by rapid ageing. Therefore the knowledge of the relevant influence factors is for a durable dimensioning of asphalt pavements a matter of particular interest. Many research studies in the past already analyzed selected influence factors on different asphalt mixtures. Thereby the influence of binder film thickness, voids in the asphalt as soon as the sort of binder and aggregates were determined. A selective analysis of multitude influence factors with identical binder and aggregate sorts by variation of the mixture composition and ageing conditions was not conducted by now. Within this dissertation selected aggregate and binder sorts were used to get mixture variations for quantifying the influence factors. For that purpose porous asphalt (PA 11) and asphalt concrete (AC 11) mixtures in combination with three sorts of aggregates (Diabase, Quartz Porphyry and hydrated Limestone Filler) and two binders (20/30 and 70/100) were chosen for the ageing under laboratory conditions with a new kind of asphalt ageing method. Also a new method for determination of the mastic film thickness of asphalt mixtures was developed. One of the findings of the analysis was that even minor changes in mixture different ageing procedures. An accelerated ageing process with porous aggregates was shown while the usage of hydrated limestone filler affected a delay of the ageing process. Also the influence of the initial stiffness of the binder sort as well as the influence of binder film thickness, binder ratio, mastic film thickness and air void ratio on the ageing was quantified. Additionally estimating functions for the prognosis of the ageing behavior were given.