Martin van de Ven

Preparation of capsules containing rejuvenators for their use in asphalt concrete

Every year, there is a demand of more than 110 million metric tons of asphalt all around the world. This represents a huge amount of money and energy, from which a good part is for the preservation and renovation of the existing pavements. The problem of asphalt is that it oxidizes with time and therefore its beneficial properties disappear. Traditionally, rejuvenators spread in the road surface, are used to restore the original properties of the pavement. The problem is that, for a rejuvenator to be successful, it must penetrate the pavement surface. Furthermore, application of a rejuvenator will reduce the skid resistance of the pavement and, besides, rejuvenators have many aromatic compounds that can be harmful for the environment. To solve these problems this paper introduces a new concept in road construction: encapsulated rejuvenators. The basic principle is that when the stress in capsules embedded in the asphalt reaches a certain threshold value, the capsules break and some rejuvenator is released, restoring the original properties of the pavement. This paper will show how to prepare such capsules and how to determine their characteristics. This is one of the first steps towards intelligent pavements.

Two Ways of Closing Cracks on Asphalt Concrete Pavements: Microcapsules and Induction Heating

It is well known that asphalt concrete is a self healing material: immediately after both faces of a crack are in contact, the diffusion of molecules from one face to the other starts. If there are no more loads, this process takes place until the crack has completely disappeared and the material has recovered its original resistance [1]. To increase this healing rate two methods are proposed. The first one is a passive self-healing mechanism. Embedded encapsulated chemicals are used in the binder. When microcracks start appearing in the binder due to the combination of ageing and accumulated damage, they break the capsules and the chemicals enter the binder by diffusion. These chemicals repair the material, decreasing the stiffness and increasing the healing rates of bitumen. The second approach makes use of an active self healing mechanism. Local heating inside the material is used to repair the binder and to improve the properties again. This is realized by adding conductive particles to the binder and using induction energy to increase the temperature. These methods are a fairly new concept in the asphalt industry.

Characterization of Organic Surfactant on Montmorillonite Nanoclay to Be Used in Bitumen

In the past decades, montmorillonite nanoclay has been used successfully to strongly improve properties of polymers. Similar improvements to nanoclay modified bitumen were expected, so the montmorillonite nanoclay was adopted to modify bitumen. To understand the interaction with bitumen, it was of fundamental importance to know the composition of organic surfactant on montmorillonite nanoclay. Two organically modified montmorillonite (OMMT) nanoclays available in the market were studied to characterize the composition of the surfactant through X-ray photoelectron spectrometry and simultaneous differential scanning calorimetry and thermogravimetric (DSC-TG) analysis. From the measurements it could be concluded that there was a difference between the surfactants. One surfactant was composed of two states of nitrogen: quaternary ammonium and probably amine or nitrile. The other surfactant only contained quaternary ammonium. In general, C—C bonds could be detected very well for the two surfactants and there were no other functional groups, such as carboxylic, hydroxyl, ketone, etc. However, it was unclear if the surfactants had C=C bonds. DSC-TG analysis indicated that the two OMMTs showed very different thermal behavior, but at temperatures below 200°C no problems were expected.

Induction Healing of Porous Asphalt Concrete Beams on an Elastic Foundation

AbstractThe objective of this paper is to evaluate the healing capacity of steel wool–reinforced porous asphalt concrete. The healing is initiated with induction heating. Bending fracture tests on an elastic foundation are used to prove the healing mechanism. Porous asphalt concrete beams on an elastic foundation were fractured at 5°C; subsequently, they were heated with induction energy, and finally fractured again. The recovered fracture resistance of the beams was used as a healing indicator. Totally fractured porous asphalt beams can regain 78.8% of their bending resistance (strength) when induction heating is applied. It was also found that the optimal heating temperature is 85°C for porous asphalt beams to obtain the highest strength recovery. Reheating of the fractured beams does not decrease the recovery of the flexural resistance, which means that the heating can be repeated when cracks return. On the basis of these findings, it is expected that the healing potential of porous asphalt concrete an...

Healing of Porous Asphalt Concrete via Induction Heating

ABSTRACT The lifetime of porous asphalt pavement is only about 11 years. In this research, a porous asphalt concrete with long lifetime, based on a healing mechanism triggered by means of induction heating, is explained. Conductive fillers (steel fibers and steel wool) are added to porous asphalt concrete to enhance its electrical conductivity and induction heating is used to increase the temperature locally, just enough to increase the healing rate of asphalt concrete to heal the micro-cracks and to repair the bond between aggregates and binder. The main purposes of this research are to examine the electrical conductivity, particle loss resistance and induction heating speed of electrically conductive porous asphalt concrete and prove that damage in the material can be healed via induction heating. It is found that long fibers with small diameter are better than short fibers with bigger diameter to make porous asphalt concrete electrically conductive, induction heatable and have high particle loss resistance as well. Finally, it is also proved that damage in porous asphalt concrete can be healed via induction heating.

Optimization of Steel Fiber Used for Induction Heating in Porous Asphalt Concrete

An electrically conductive porous asphalt concrete used for induction heating and subsequently healing of cracks is prepared by adding conductive materials (steel fibers and steel wool) in this research. In this paper, the optimization of steel fiber used for induction heating is reported based on the electrical resistivity, induction heating speed and particle loss resistance of porous asphalt concrete. It is found that porous asphalt concrete containing steel fiber with smaller diameter or longer steel fiber is more electrically conductive and induction heatable than that containing the same content of steel fiber with bigger diameter or short steel fiber. It is also found that steel wool type 00 with length of 9.5 mm is more effective than short steel fiber type 1 and steel wool type 000 to improve the particle resistance of porous asphalt concrete. Finally, 8% (by volume of bitumen) of steel wool type 00 is considered as the best option used for induction heating in porous asphalt concrete.

Hot Recycling of Bituminous Mixtures

This chapter first presents the results of a survey perfomed on the practices used in Europe. This survey is first report on the subject and could be usefully completed by the states of the art prepared in the framework of the Re-road and Direct-Mat European projecys.

Crack-Healing Investigation in Bituminous Materials

Self-healing is one of the great potential processes for service-life extension of asphalt pavements. However, the underlying mechanism is not explained, and a proper way to measure it is not mentioned. It is necessary to understand the self-healing mechanism and to develop a setup to measure it. In this paper, the self-healing process was hypothesized as the reverse process of cracking. Three new test methods were developed to mimic the self-healing process of cracks in bituminous materials (including bitumen, mastics, and asphalt mixtures) in the laboratory. The results indicate that the proposed crack self-healing assessment methods are capable of ranking the self-healing capability of bituminous materials. The crack self-healing process contains two important phases, namely, crack closure and strength gain. The occurrence of these phases is dependent on healing time and temperature.

Self-healing characteristics of bituminous mastics using a modified direct tension test

Cracking is one of the main distresses responsible for the service life reduction of asphalt pavement. On the contrary, self-healing is a process that reverses to cracking and increases the service life. Understanding of the cracking and healing behavior of bituminous materials is very important for service life predictions. Instead of a complex and time-consuming fatigue test, a modified direct tension test with a loading–healing–reloading procedure was developed in this article to characterize the cracking and healing behavior of bituminous mastics. A displacement-controlled loading was applied to obtain damaged specimens with different crack sizes at various postpeak elongations. After unloading and healing, the reloading was applied to quantify the healing behavior under different conditions. The healing behavior is very dependent on rest periods, crack phases, and material types. A clear difference in self-healing property between a polymer-modified bituminous mastic and a conventional penetration grade bituminous mastic was observed for different phases of crack. As a result, the modified direct tension test is believed to be an effective tool for characterizing the self-healing capability of bituminous mastics.

Knowledge Discovery and Data Mining Using Artificial Intelligence to Unravel Porous Asphalt Concrete in the Netherlands

The main goal of this study was to discover knowledge from data about Porous Asphalt Concrete (PAC) roads to achieve a better understanding of the behavior of them and via this understanding improve pavement quality and enhance its lifespan. The knowledge discovery process includes five steps, being understanding the problem, understanding the data, data preparation, data mining (modeling), and the interpretation/evaluation of the results of the models. At the moment, almost 75% of the Dutch motorways network has a PAC top layer. The main damage of PAC is raveling, which is when the top layer of the road loses stones. The SHRP-NL databases provided ten years of material property data from PAC roads. The data for climate and traffic were obtained from databases of the Royal Dutch Meteorological Institute (KNMI) and the Ministry of Transport and Water Management, respectively. Due to the low number of data points (74 data points), an extensive variable selection was performed using eight different methods to determine the four or five most influential input variables and consequently reduce the input dimension. These methods were decision trees, genetic polynomial, artificial neural network, rough set theory, correlation based variable selection with bidirectional and genetic search, wrappers of neural network with genetic search, and relief ranking filter. The modeling step resulted in 8 intelligent models which were developed using two prediction techniques, being artificial neural networks and support vector machines and two rule-based techniques, being decision trees and rough set theory. Taking the low number of data points into account, the prediction models showed a good performance (R2 = 0.95). The rule based models were transparent and easy to interpret but performed less.