Bio-polymer modified bitumen

Bitumen is a key constitutive material in asphalt pavements. It binds together the rock scaffolding of a pavement. Bitumen provides asphalt pavement with flexibility and enables it to respond to traffic loading and return to its original condition after the loading, i.e. bitumen restores/repairs the damage. In Porous Asphalt (PA) or...

Bio-Oils as Asphalt Bitumen Rejuvenators

Bitumen rejuvenators are used to improve or restore the physical and mechanical performance of aged bitumen. Traditional bitumen rejuvenators are a product of crude oil. As crude oil production declines and the environmental and financial costs of crude oil increase, there is an urgent need to identify more environmentally sustainable bitumen...

Value of evidence in the rare type match problem: Common source versus specific source

In the so-called rare type match problem, the discrete characteristics of a crime stain have not been observed in the set of background material. To assess the strength of evidence, two competing statistical hypotheses need to be considered. The formulation of the hypotheses depends on whichidentification of source question is of interest ...

Overall mean estimation of trace evidence in a two-level normal–normal model

In the evaluation of measurements on characteristics of forensic trace evidence, Aitken and Lucy (2004) model the data as a two-level model using assumptions of normality where likelihood ratios are used as a measure for the strength of evidence. A two-level model assumes two sources of variation: the variation within measurements in a group ...

The influence of boundary conditions on the healing of bitumen

Damage in pavements is known to reduce over time when the material is left to rest, this phenomenon is identified as healing. It has been shown that healing has a large influence on pavement performance. However, as the healing mechanism is not fully understood, there is currently no accepted method available to assess the healing performance...

Het healingmechanisme van bitumen nader verklaard

Asfalt heeft de aantrekkelijke eigenschap dat het zichzelf kan herstellen na schade. Er is echter tot op heden geen betrouwbare methode om de healingcapaciteit van een asfaltmengsel te bepalen. Bij het healingproces van een discrete scheur spelen twee processen een rol, namelijk het in contact komen van de oppervlakken van de scheur; het...

Direct Tensile Test to Assess Healing in Asphalt

Asphalt concrete has the advantageous ability to heal. During rest<br/>periods, damage present In the material is restored to a certain extent.<br/>Healing of the material can be observed in iis regaining of strength<br/>and stiffness after rest periods. In this paper, a new test method is presented.<br/>It was developed to increase the...

The importance of wetting in healing of bitumen

Asphalt concrete has the advantageous ability to heal autonomously, however the mechanisms behind this are not fully understood. To increase insight in the healing mechanism, the healing model used in polymer science is adopted. It interprets healing as the sum of wetting and intrinsic healing. The presented work introduces a new test set-up,...

Mechanisms in Healing of Bitumen and the Impact of Normal Force

Damage in pavements is known to reduce over time when the material is left to rest, this phenomenon is known as healing. It has been shown that healing is an important influence factor in pavement performance. However, an accepted method to assess the healing capability of a pavement is currently not available. Healing of cracks is assumed to be...

Healing van Asfaltmengsels: Onderzoek naar een pragmatische proefmethode

Het zelfherstellend vermogen, of de healingscapaciteit, van asfaltmengsels wordt in de meeste ontwerpmethoden voor wegverhardingen meegenomen. De kennis over dit zelfherstellend vermogen is gebaseerd op ervaringen en onderzoeken uit het verleden en de werkelijke mechanismen erachter zijn niet bekend. Hierdoor is het moeilijk om voor nieuwe...

High filler concrete using fly ash: Chloride penetration and microstructure

Most high filler concrete studies are based on relatively high contents of powder (cement + filler) (>400 kg m-3). This paper aims to increase the total fly ash content relative to the clinker content, while simultaneously minimizing the total powder content in the concrete to values lower than 300 kg m-3. The motivation for decreasing the total...

Chloride penetration into cementitious mortar at early age

Modern service life design methods for concrete structures use chloride diffusion data as an input parameter. Abundant data exist for concrete at 28 days and, to a lesser extent, at later ages. This paper presents chloride diffusion data for mortar at ages between 1 day and 28 days age. Rapid Chloride Migration (RCM) and natural diffusion tests...

Service life and life cycle cost modelling of cathodic protection systems for concrete structures

Corrosion of reinforcing steel in concrete structures causes concrete cracking, steel diameter reduction and eventually loss of safety. In infrastructure this is mainly due to penetration of chloride ions from de-icing or marine salts. Conventional repair means heavy, labour intensive and costly work and economic pressures (time and money) work...

Divacancies and the hydrogenation of Mg-Ti films with short range chemical order

We obtained evidence for the partial chemical segregation of as-deposited and hydrogenated Mg1?yTiy films (0 ? y ? 0.30) into nanoscale Ti and Mg domains using positron Doppler-broadening. We exclusively monitor the hydrogenation of Mg domains, owing to the large difference in positron affinity for Mg and Ti. The electron momentum distribution...