07 – Multi-Functional Transport Infrastructures Training Week, Paris/Nantes – France, Monday 21th to Friday 27th of January 2019

 SMARTI Fellows ... Winter has come ... keep walking ... never look back .! 

Hello word...!!

Before we get into the main topic of the post, I would like to thank you all, pavement lovers, because we are now getting closer to pass the first milestone of the blog. We are approaching the 2,000 views and I am extremely pleased to tell you that there are viewers from all over the word, from Chile to New Zealand. Next milestone is to double the viewings before the end of the year so I count on you to make it happen.!

Well, let’s get back on “track”. On this occasion, I will be taking you to two of the most beautiful cities that Europe has, Paris and Nantes. As part of our training activities, the SMARTI ETN Consortium met once again for the third training week. The theme was Multi-Functional Transport Infrastructure and the locations for the meetings could not be better. In Paris, we were at  The École Nationale des Ponts et Chaussées (National School of Road and Bridges). This well-known and prestigious school is one of the oldest in France and for a pavement engineer such as myself, a dream come true. The school was created in 1747 under the name of École Royale des Ponts et Chaussées by Daniel-Charles Trudaine, Civil Engineer and one of the primary developers of the present French road system. On Wednesday afternoon, we travelled to Nantes to visit The French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR), some of you might remember them from a previous post.

I could not resist to take a "selfie" at the entrance of such a prestigious School.

Every time that we, Early Stage Researchers (ESR), get together, we start by doing a group activity called “speed-dating” where we have the opportunity to put everyone up-to-date in the development of our projects. This time, Ana Jimenez del Barco Carrion who is the Project Manager, have a brilliant idea and grouped the researchers with similar projects or visions which to me made more sense when discussing progress and difficulties. As a result, we have managed to collaborate between ourselves and send an abstract call “Towards more sustainable Pavement Management practices using embedded sensor technologies” submitted to Infrastructure Open Access Journal under the SMARTI Special Issue. We all saw it as an opportunity to create conscience and see how our research life’s will continue once this wonderful experience comes to and end. So far, we are still having meetings and we have agreed on finishing the paper by the end of summer.

During our stay in Paris, we had a guide visit to “Sense-City”, a 9 million euros Facility for ANR’s Future Investment Program. Sense-City is a state-of-the-art climate chamber that can cover two 400m² areas (mini-city) equipped with sensors to study the performance of facilities and urban materials, monitor the city of tomorrow by sending appropriate information, and study air, water and soil pollution. We had a live demonstration on different projects but the most impressive was to see how they can simulate the sun-hours and its effect on the roads/houses/air/vegetation. One of the things that other fellows and I discussed was on the effect that this type of research has on the environment. We understand that in order to create something new, it needs to be studied and proved, but some of us believed that there was an excessive use of resources. Nonetheless, we hope the project keeps evolving and we look forward to seeing the results in the near future. Equally interesting was the presentation on Nano-technology and its use on civil engineering applications. SMARTI ESR-2 works with its solution and if you have been following my research will find some similarities.

With an old friend, Søren Rasmussen, from Dynatest Denmark and our guided visit to Sense-City.

In order to warm-up things, we had an internal competition called “Infra-hackathon”. We were asked to present a solution to a current mobility problem where we needed to increase the number of travellers without increasing the number of cars. Also, we needed to find a way to finance the project as there was not budget from central government and adding tolls was not an option. Wind energy harvesting was the most popular option among the groups as a way to make the infrastructure self-powered as well as smart barriers for traffic distribution. I guess the objective was to make the ESR’s think on how current infrastructure could be transformed to serve more than one purpose in the future.

The challenge: Infra-hackathon. Thanks Emmanuel.!

Finally, we had a guided visit to IFSTTAR Nantes where the concept Accelerated Pavement Testing (APT) was presented to us. Pier Hornych, LAboratory for Modelling, Experimentation and Survey of transport infrastructures (LAMES), introduced the Fatigue Carrousel and walked us through the process of designing, constructing, measuring, and modelling an APT experiment which was a lifetime experience for some of the ESR’s, specially for those who work/love pavement engineering. Personally, it was an enrichment experience to have a third visit to the carrousel and a motivation/challenge to promote this type of research back in my home country, Ecuador.   

Pier Hornych and Juliette Blanc walking us though the concept of APT.

SMARTI ETN group photo during our visit to the Fatigue Carrousel.

Well my beloved pavement lovers, I guess it’s time to end this post but keep in touch for more exciting news on the development of my project...!

Mario Manosalvas Paredes.

05 – Accelerated Pavement Testing at IFSTTAR, Nantes – France, Mon 14th Apr – Fri 18th Apr, 2018 & Mon 08th Oct – Fri 12th Oct, 2018

Hello word...!!

I hope that you are liking the blog. This is the fifth entry that I am making and just between us, I am getting used to it 😊. However, you have let me do all the “talking” and have not interacted with me which was one of the goals I had when I started blogging. Thus, I encourage you to share your thoughts, ideas, likes, dislikes under the comment tab at the end of the post.

On this occasion, I am writing about the two-work visits I had to the Fatigue Carrousel which is an Accelerated Pavement Testing (APT) facility owned by The French Institute of Science and Technology for Transport, Development and Networks (IFSTTAR). For those who know about what APT is and have hear about what IFSTTAR does then the next lines might be redundant; on the other hand, for those who are curious, specially for those with a pavement engineering orientation, I hope that you will continue searching on your own and perhaps in the near future we could have a discussion.

Figure 1: IFSTTAR Nantes.

John Metcalf under NCHRP: Synthesis of Highway Practices 235 “Application of Full-Scale Accelerated Pavement Testing” in Chapter 1, page 3 defines APT as “the controlled application of a prototype wheel loading, at or above the appropriate legal load limit to a prototype or actual, layered, structural pavement system to determine pavement response and performance under a controlled, accelerated accumulation of damage in a compressed time period” (Metcalf, 1996)” while IFSTTAR is a public research institution created in 2011 as a result from the merger of The French National Institute for Transport and Safety Research (INRETS) and the French Central Laboratory of Roads and Bridges (LCPC). IFSTTAR is composed by five departments: MAST, GERS, COSYS, TS2, and AME which can be seen by clicking the links.

There is some background information regarding the project that I am omitting in order to not make the post too extensive. Having say that, from now on, I will be a little bit more technical in order to describe what was the real purpose of my visit to Nantes. During the first seven months of my research I focused on literature review on piezoelectric materials, sensors, pavement performance, pavement modelling, damage modelling, basically in everything that could be related to link pavement responses to predict its future condition. In parallel, during one meeting with my research supervisor, he told me that our piezoelectric sensors, from now on PZT, were installed on the Fatigue Carrousel and that I should get ready to handle it. Until that point, I have not seen the PZT’s so I was more than ready to travel to Nantes to get the data and to have a brief introduction of the experiment.  Figure below shows the first I saw both PZT Carrousel.   

Figure 2: PZT developed at Michigan State University (MSU), USA.

Figure 3: Fatigue Carrousel during installation.  

APT was carried out between November 2017 and February 2018 where 1.0 million loads were applied. Temperature was measured at different depths (0.0, 50.0, and 100.0 millimetres). Wandering was studied through eleven positions, equally spaced, with a total length of 1.05 meters; position six was at the centre with radius 19.00 meters. Traffic followed a Gaussian distribution where position six bear 22% of it.  Following figures show how data was treated, from importing raw measurements to define an average signal, to then plot maximum values across the transverse position where wandering can be seen.   

Figure 4: Raw voltage after 500,000 load repetitions at radius 19.00 meters.

Figure 5: Average voltage after 500,000 load repetitions at radius 19.00 meters.

Figure 6: Strain responses from TML Gauge at 100 mm depth.

Figure 7: Voltage responses from PZT at 100 mm depth.

Finally, I cannot end this post without my moment of fame, respective selfie, on the Carrousel. In case you wonder, I used MATLAB (90%) and Excel Macros (10%) for processing the data. 

Figure 8: Your blogger with his respective selfie.

Long nights, such as this one, have gotten me closer to the main goal, The PhD.! Stay tuned and see you soon pavement lovers!

Mario Manosalvas Paredes.

02 - 1st Training Week, University of Nottingham, Mon 12th Feb - Fri 16th Feb, 2018

“Alone we can do so little, together we can do so much.”

Helen Keller

Hello word...!!

This time, I would like to take the opportunity to tell you about the first time we met as SMARTI ETN . Our group was made up of 14 researchers and more than 30 transport professionals from both academia and industry. Our 1^st SMARTI Training Week was hosted at the University of Nottingham from Monday the 12^th to Friday the 16^th of February and it was an excellent opportunity to know the other researchers as well as the partners of the projects which gave us a good idea of how this amazing experience will impact our lives and careers. As mentioned before, SMARTI is a training network which means that, it is more than a normal PhD program. For us, being part of SMARTI is an opportunity to learn what research is and to understand how we can relate research projects to industry. We have been told that during the next 3-years, we will gain soft skills that can be used both in academia or industry which was one of the many reason I decided to apply for this position.

During our first meeting which was called “Introductory week on Transport Infrastructures” we took part of intense activities and educational games organized with the aim of strengthening the unity between the early stage researchers (ESRs). Some of the concepts that were introduced to us comprise railways and pavement design, construction, maintenance and operation, materials, risk and reliability, sustainability and climate change. The lessons were taught by professors from the Nottingham Transportation Engineering Centre (NTEC) as well as by professionals from Industry. 

Discussing with Maria and Natasha about the similarities of our projects. 

Finally, I would like to say thank you to SMARTI and to the University of Nottingham for organizing such a great training week, to the lectures and my other colleagues that participated. Looking forward to participating in the oncoming training weeks!

Stay tuned and see you soon pavement lovers!

Mario Manosalvas Paredes

01 - Why avements deteriorate?

“The road to success is paved with the hot asphalt of failure.”

Craig D. Lounsbrough

Hello word...!!

As it was mentioned in my previous post, here we will go through some concepts regarding the deterioration of pavements. Feel free to express your point of view. The aim is to share knowledge and to understand how different people sees pavement engineering so let's start.

It is well known that pavement deterioration is caused by the interacting damaging effects of traffic loading, environment, materials and failure criteria. Could it be that we are missing something between these colossal factors? What are the consequences of not applying maintenance plans to our pavements and perhaps more important, who will suffer the after-effect? The aim of this post is to provide an overview of the damaging effects that pavement engineers need to face in everyday situations and propose alternative solutions to overcome them. Traffic loads and their impact on pavements are quantified in terms of axle loads, timing of axle passes, axle lateral placement, tyre inflation pressure and number of repetitions. Axle loads, axle configuration and load magnitude are deeply connected between themselves. Axle configuration is defined by the number of axles sharing the same suspension system and the number of tyres in each axle which can be referred to as single, tandem, triple, or quad. Besides the single axle, all the other configurations need to be treated differently since the transmitted load in terms of stresses and strains will overlap in the pavement. The timing of axle passes is important for both flexible and rigid pavements, mainly because of the seasonality in pavement layer properties and the time dependency of thermal stresses, respectively. The vehicle speed, axle speed, is relevant mainly to flexible pavements due to the viscoelastic behaviour of the asphalt concrete as well as the lateral distribution of the accumulated damage because of the weaving effects. When reviewing the number of repetitions there are two well-defined paths that can be followed, firstly, the widely accepted procedure which develops equivalent factors and converts each load group into an equivalent single-axle load (ESAL – 80 kN) and secondly, the consideration of multiple axles which is not a simple matter as it could lead out to an unsafe procedure if the tandem and triple axles are treated as a group and considered as one repetition or on the other hand lead to a too conservative procedure if each axle is treated independently and considered as one repetition. All in all, traffic loads, primarily those from heavy trucks, cause stresses/strains in pavement structures, whose effects accumulate over time resulting in pavement deterioration such as plastic deformation in asphalt concretes or fatigue cracking in Portland concretes.

Regarding how the environment influences the pavement, let me refresh the concepts of climate and weather before we get into detail. Climate is defined as the regular weather conditions for an area where the weather is the day to day manifestation of this climate. History has demonstrated, sometimes with pathetic examples, that weather has always been one of the primary factors that affect the pavement. Factors such as temperature, frost and thaw, moisture and precipitation play major roles affecting the elastic moduli of the different layers within the structure. In hindsight, every pavement structure has been designed based on historical climate however, during their design life a very different condition could occur therefore not taking this into consideration could be vast in terms of pavement performance, disruption to traffic and public safety just to name a few. There are also less obvious effects on pavement deterioration caused by the increase in average temperature and changes in rainfall patterns therefore the use of adaptive maintenance practices such as permeable pavements, polymer modified binders and improved routine maintenance of joint seals is encouraged. In the near future, in order to minimize the disruption caused by weather changes, it will be crucial to plan and adapt to the changing climate rather than base decisions on the climate we experienced in the past.  Figure 1, categorize the different variables that can be found in the design per importance degree; as it was stated before, temperature, precipitation, wind and soil moisture are the main variables that as pavement engineers need to consider.

Figure 1: Climate variables relevant to highway maintenance

      

Henceforth, materials will be analysed and most importantly, the impact that they cause on the performance of our structures will be discussed. When relating materials to pavement deterioration, it is almost automatic to think about the construction process and to even agree that in most of the occasions, the issues related to the early appearance of distress come from poor construction quality. Going a little bit deeper, the after-effects that we face in our pavements namely distress can easily come from an improper grading of aggregates for base or subbase or from a poor subgrade soil of low bearing capacity, which for some readers could not even be imaginable. Another interesting point of view is the use of marginal or second-rate base materials for pavement construction due to geological conditions of the area which may provoke or accelerate deterioration resulting in rutting, cracking and shoving or combinations of these problems. All in all, failure to obtain proper compaction, improper moisture conditions during construction, quality of materials and accurate layer thickness after compaction will deteriorate over time the performance of a pavement. Figure 2, shows a general overview of these problems.

Figure 2: Climate variables relevant to highway maintenance  

        

The objective with the design of a pavement structure is to avoid the excessive flexing of any layer, failure to achieve this will result in the over stressing of a layer, which ultimately will cause the pavement to fail. In both flexible and rigid pavements, the load distribution pattern changes from one layer to another due to the strength differences. The top layer is considered the least flexible therefore will be the strongest material since the load is applied to a small area (surface of the wheel) resulting in high stress levels; based on the same analogy, the lower layer will be the most flexible therefore the weakest material because the load is applied in a larger area resulting in lower stress levels, see Figure 3.  

In the past, empirical pavement design methods were use based on observations of performance in pavements with known dimensions and materials under specific climatic, geologic and traffic conditions. The outcome seen by many engineers was that this method led to overly conservative designs. Nowadays, mechanistic qualities have been added to the empirical design philosophy resulting in the Mechanistic-Empirical (M-E) design methods to determine the stresses, strains and deflections a pavement will experience from external influences and an empirical relationship to connect pavement response with pavement deterioration. The implementation of M-E will allow pavement engineers to design our structures with the right thickness for the specific conditions in each geographic area. It is fundamental that we recognize that pavement design and the type of selection process is dynamic and will change as more data is gathered and more lessons are learned.

  

Figure 3: Load distribution of flexible and rigid pavements      

      

To conclude, if knowing the damaging effects that the exposed factors produce to our pavements, why do we still see early distress in our projects? Is it because the gap between the practical-theoretical knowledge and the constructional process is that big, that even with understanding the behavior, we cannot place it on the field and that the only way to overcome this situation is through intensive research both from the Academia and the Private sector. Limitations such as not using high-quality materials due to the location of the project should not be a barrier to our designs, at least not anymore since we could overcome either by modifying existing materials with recycling techniques or by creating new materials where most of the mechanical, physical and chemical properties could be designed to withstand the adverse weather and loading conditions. In the near future, we should not allow poor construction processes to be a factor that can deter the development of our structures; it would not matter to have the most resistant materials if we cannot place them correctly on site. The beauty, as I see it, is that most of the lessons have been learnt from past experiences; we are entering a new era where new techniques will come into play and we need to be prepared to face them and to use them to our best interest; which as pavement engineers, we should not forget the end goal, minimize the total cost to society.

That's all from today. Stay tuned and see you soon!

Mario Manosalvas Paredes