Wim Van den bergh

The influence of nanoclay on the durability properties of asphalt mixtures for top and base layers

To avoid traffic congestion, due to road works, a continuous research into asphalt pavement and especially its durability is of great importance. This research focuses on improving the mechanical performance and the durability of asphalt mixtures by nanoclay modified bitumen. This promising technique of introducing nanoclays or nano particles into bitumen could offer an significant improvement on the fatigue properties and rutting performance and thus the durability of the asphalt top layer.

Digital Image Correlation to Investigate Crack Propagation and Healing of Asphalt Concrete

Accurate determination of the mechanical properties of asphalt concrete is very important in Road Engineering. The traditional method to calculate these properties is to run experiments using a hydraulic/pneumatic actuator and strain gauges to apply stress and measure the strain. However, in the last decade optical measurement techniques have become popular for strain calculation on the surface of the specimen and detecting the cracks on the surface. In this study, digital image correlation is used to estimate the strain map on the surface of an asphalt specimen, predict the location of crack initiation, and investigate the healing phenomenon in asphalt concrete.

Peat as an Example of a Natural Fiber in Bitumen

In this study, the suitability of a natural peat fiber, as a modifier for bitumen was investigated. Peat fibers were dried, ground, and fractionated into a fiber and a granular fraction. Rheological data on peat modified binders indicated that the granular fraction is acting as a filler mainly stiffening the bituminous binders whilst the fiber fraction mainly increases the elastic behavior, which became especially visible at higher service temperatures. It was observed that by changing the ratio of fibers versus granular particles, the rheological behavior can be regulated. In addition, drainage tests were carried out on stone mastic asphalt (SMA) mixes. The data indicated that peat fibers can effectively reduce drainage, and can be used as an alternative for the currently used cellulose fibers.

Reuse of bituminous pavements: A mini-review of research, regulations and modelling

Bituminous pavement can be recycled – even multiple times – by reusing it in new bituminous mixtures. If the mechanical properties of the binder get worse, this reclaimed asphalt is often used in the sub-structure of the road. Apparently, up till now, no end-of-life phase exists for the material. Actually, defining the end-of-life and the end-of-waste stage of a material is important for life cycle assessment modelling. Various standards and scientific studies on modelling life cycle assessment are known, but the crucial stages are not yet defined for reclaimed asphalt pavement. Unlike for iron, steel and aluminium scrap, at this moment, no legislative end-of-waste criteria for aggregates are formulated by the European Commission. More research is necessary in order to develop valuable end-of-life criteria for aggregates. This contribution is a mini-review article of the current regulations, standards and studies concerning end-of-life and end-of-waste of reclaimed asphalt pavement. The existing methodology in order to define end-of-waste criteria, a case study on aggregates and the argumentation used in finished legislative criteria are the basis to clarify some modelling issues for reclaimed asphalt material. Hence, this contribution elucidates the assignment of process environmental impacts to a life cycle stage as defined by EN15804, that is, end-of-life stage (C) and the supplementary information Module D with benefits and loads beyond the system boundary.

The use of a non-nuclear density gauge for monitoring the compaction process of asphalt pavement

The mechanical performance of an asphalt pavement affects its durability – thus carbon footprint. Many parameters contribute to the success of a durable asphalt mix, e.g. material selection, an accurate mix and even the road design in which the asphalt mix quality is quantified. The quality of the asphalt mix, by its mechanical properties, is also related to the compaction degree. However, and specifically for high volume rates, the laying process at the construction site needs an effective method to monitor and adjust immediately the compaction quality before cooling and without damaging the layer, which is now absent. In this paper the use of a non-nuclear density gauge (PQI – Pavement Quality Indicator) is evaluated, based on a site at Brussels Airport. Considering the outcome of the present research, this PQI is advised as a unique tool for continuous density measurements and allow immediate adjustments during compaction, and decreases the number of core drilling for quality control, and as a posteriori asphalt pavement density test where cores are prohibited. The use of PQI could be recommended to be a part of the standard quality control process in the Flemish region.

Recommendations and strategies for using reclaimed asphalt pavement in the Flemish Region based on a first life cycle assessment research

In Flanders, using Reclaimed Asphalt Pavement (RAP) is allowed in asphalt mixes for base layers. Primary economic and secondary laboratory-measured mechanical properties are given as justification for higher amounts in specific mixes. However, one should evaluate the performance of these mixes on long-term by environmental impact of the production until end-of-life. In this paper recommendations and strategies for using RA, based on current research, are discussed in a broader perspective such as using a carbon-footprint tool and warm-mix asphalt production in the Flemish Region. The paper aims to a wide discussion by reporting several outcomes of laboratory research, statistics and practical application in order to set a general strategy for the road engineering sector in the Flemish Region.

The influence of mixture composition, adhesion promotor and compaction degree on the groove stability of grooved Marshall asphalt

After the first rehabilitation of runway 07R/25L in 2015, runway 01/19 was reconstructed in the summer of 2016, as part of a cycle where all runway pavements at Brussels airport are completely renovated each thirty years. The top layer is a Marshall asphalt with a polymer modified bitumen. To optimize the water drainage the central part of the runway (47 m wide) is grooved instead of applying an anti-skid layer. In this paper the focus is on the durability of the grooved top layer. Two different Marshall asphalt mixtures with a different maximum granulate size (10 mm or 14 mm) are compared, both in the laboratory and in a full-scale trial. In the laboratory the resistance against rutting and raveling are investigated for both mixtures with and without adhesion promotor, which did not show a positive effect. In the full-scale trial the compactability and impact of both a longer curing period and a variation in the degree of compaction on the groove stability is investigated for both mixtures using a heavy truck. No visual differences could be found except in areas which were undercompacted and showed more damage to the grooves.

Identification of pavement material properties using a scanning laser Doppler vibrometer

This paper presents an inverse modeling approach to estimate mechanical properties of asphalt concrete (i.e. Young’s modulus E, Poisson ratio ν and damping coefficients). Modal analysis was performed on an asphalt slab using a shaker to excite the specimen and an optical measurement system (a Scanning Laser Doppler Vibrometer or SLDV) to measure the velocity of a measurement grid on the surface of the slab. The SLDV has the ability to measure the vibration pattern of an object with high accuracy, short testing time and without making any contact. The measured data were used as inputs for a frequency domain model parameter estimation method (the Polymax estimator). Meanwhile, natural frequencies and damping ratios of the system were calculated using a Finite Element Modeling (FEM) method. Then, the Modal Assurance Criterion (MAC) was used to pair the mode shapes of the structure determined by measurements and estimated by FEM. By changing the inputs of the FEM analysis (E, ν and damping coefficients of the...

Climate change impact compared to life cycle assessment results : a pilot case in Flanders

In 2013, a pilot project ‘Carbon Free-Ways’ was elaborated in which the Flemish government included both price and CO2 emissions as award criterion in a public tender for the reconstruction of a field case in Kontich (Belgium). The road works include the construction of a base course with 50% reclaimed asphalt pavement and a surface course with 100% virgin split mastic asphalt, both are warm asphalt mixtures. Data was measured during the execution of the works for raw materials, transport and asphalt production. This real live data is used for all calculations. The approach used in the pilot project (Carbon Counter tool) to assess the emissions from the road construction is compared to a comprehensive environmental analysis following the life cycle assessment methodology. This paper aims to answer the following four main research questions. What is the difference between the results from the Carbon Counter and the life cycle assessment calculation? What is the contribution of climate change impact to the total single score environmental impact? Which materials or processes have the highest environmental impact? What is the environmental impact of processes which are beyond the scope of the pilot project? It was found from the current study that CO2 emissions or climate change impact is for sure not the only important environmental impact. Fossil depletion was found to majorly contribute to the total single score impact and transport by lorry and the raw material bitumen are processes and materials with an important contribution to the environmental impact.

Recycling reclaimed asphalt in Flanders: state of the art 2014

This contribution illustrates the state of the art of the use of reclaimed asphalt pavement (RAP) in bituminous mixtures for roads in Flanders. A first part will give a summary of the supply of reclaimed asphalt and its use for the last decade in Flanders. Different mixtures with the use of RAP are compared by means of stiffness and fatigue properties. In Flanders, the regulation and the composition of asphalt is different for non-public and public works. For the latter, the Flemish Regulation must be followed and till 2011 recycling was allowed both for mixtures for base and surface layers, up to 50% binder substitution. However, after 2011 recycling became prohibited for top layers. Since 2013, the Flemish Agency for Road and Traffic and the University of Antwerp started an experimental program to evaluate the limited use of reclaimed asphalt in mixtures for surface layers, e.g. AC-10 and SMA. A LCA study showed that the use of RAP is beneficial compared to the use of warm mix asphalt. Further, in this paper, the results of this experimental program for AC-10 and SMA with RAP are discussed. The study recommended allowing the use of RAP up to 50% for AC-10. In a second project, the performance characteristics of SMA mixtures (SMA-C1 with 70/100 and SMA-C2 with 45/80-50) with reuse of reclaimed asphalt pavement are explored. The experimental study of the performance characteristics consist of % Voids, resistance to water sensitivity, rutting, stiffness modulus and ravelling (Darmstadt scuffing device prTS12697-50). The study showed that the addition of RAP has no negative effect on the performance of the mixtures. The contribution concludes with a recommendation to re-evaluate the prohibition of RAP in surface layer mixtures.