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    Posted 08-07-2020 09:01 AM
    Edited by Tirza Austin 08-07-2020 03:10 PM
    Good day,

    My name is Kelvin Marumba and I am working as a Research Scientist in Zimbabwe. The major problem on our road is dealing with the issue of unbearable potholes and I am sure this is also an issue in other developing countries. I am seeking assistance in different types of ways to solve this issue or rather solutions and methods I can use to patch these potholes and get a longer lifespan. Which mixture of materials can I use to patch them up or what materials can I look into or research into? We are trying to avoid expensive methods and have a temporary solution with a longer lifespan for patching up the potholes. I look forward to your favorable responses.

    Kind regards,

    Kelvin Marumba Aff.M.ASCE


    Posted 08-09-2020 08:47 PM

    The solution to problem of poor road conditions is not one of technology, it is one of government policy.

    When a road is built, especially in jurisdictions where finances are constrained, the road has a certain pavement structure, usually the less expensive option. However, less expensive options usually require more maintenance, especially preventive maintenance. Very few road authorities acknowledge that they do not have the means to carry out the required maintenance. Whether this happens by error or omission, the end result is the following sequence of events: pavement deteriorates, preventive maintenance is not performed, cracks appear, regular maintenance is not performed, cracks join and potholes appear, rehabilitation is not performed, and the road goes into accelerated deterioration. At this point crews are dispatched to try to patch the potholes but since this is years too late, the repairs will not last.

    Additionally, because there are political interests in the administration of the infrastructure, the budget tends to concentrate in the paving of as much road as possible for as little money as possible. This approach tends to ignore the works which actually make the road stay in good condition, such as adequate drainage (which in many cases requires land acquisition), weight limitation enforcement of commercial vehicles, subdrainage to avoid elevated levels of moisture in the subgrade, and stabilization (chemical or with geogrid) of the areas of poor subgrade.

    In jurisdictions where it does not snow, in my experience, (and the research can bear this out), the solution to solving the road condition problem is as follows:
    1.- Use long design periods (30yrs for main roads). This results in a flatter deterioration curve, so maintenance schedules can be more flexible. 
    2.- Use long lasting pavements. From my personal experience, concrete pavements have yielded the best value. 
    3-  Use a layered approach. There is a tendency to focus only on the top layer, but best results are obtained from the use of high performing bases: e.g cement stabilized, and improved subgrades, e.g. lime stabilized
    4.- Ensure drainage and subdrainage performance. Subdrains, permeable bases, lined ditches, etc. are a few of the tools to be considered.
    5.- Provide routine maintenance. This includes vegetation removal, culvert cleaning, ditch maintenance, etc.

    The above scheme elevates the up-front cost, but reduces the maintenance significantly, and tends to avoids major deterioration for a long period. Roads such as the Mediterranean freeway in Valencia are more than 60 yrs old without major deterioration (although it has excellent maintenance), and the Airport highway in El Salvador is 20 yrs old without a need for major repairs (potholes or severe cracks).

    How is this scheme of preventing (rather than repairing) the potholes achieved in practice? It requires a bold new thinking in the local engineering community, to be able to show governments that yes, the price of long lasting infrastructure is high, but the cost to society of not having it is even higher (and by orders of magnitude), since the state of infrastructure disrepair impacts industry investments, vehicle operating costs, freight prices and many aspects which noticeably increase the cost of local goods and services. If this can be conveyed to political officials, it becomes a matter of finding the appropriate financial tools, of which there are many: Public private partnerships, shadow toll roads, infrastructure banks, development banks, maintenance concessions, etc. 

    To sum up, you would be surprised how much policy can achieve if it is has sound technical foundations.

    Let me know if you would like to discuss further.

    Sergio Fernandez, P.Eng.
    Calgary, Alberta,

    Sergio Fernandez M.ASCE
    Senior Transportation Engineer
    Calgary AB


    Posted 08-31-2020 04:49 PM
    You have already gotten good advice.  I will add that even good pavements will lose oil over time. Once water jetting has removed so much oil that the pavement lets water penetrate the pavement section, this is the beginning of the end of your pavement.  Alligator cracking will start because the water in the subbase reduces the load capacity of the pavement. The cracks then allow more water to soften the substrate.  The solution is to use a surface sealer such as a sand or chip seal before the pavement becomes poris.  When you get a lot of potholes your base is already gone and it is time to evaluate I'd you can get away with an engineered fabric and overlay or if it is time to grind your pavement to make base material for a new road section. Any streets that have potholes that are not utility related should be evaluated for surface sealer. 

    If you only have an isolated area that has gone bad, then the most important thing is to over excavate and install a well designed base section before repairing the pavement.  The key is to remove failed subbase and if dry enough conpact thoroughly, before adding any base material.  You then should make sure to finish your patch with a sealer that will protect the edges from cracks reflecting to the surface at the joint.  Failure at the joint will start your problems all over again.  I recommend that patched areas be revisited in six months and resealed again if the joint is noticable.  

    In France main rural roads are sealed on a regular basis and rarely need repair.  In the long run, this is the most cost effective way to manage pavement maintenance.  

    Barbara A.B. Salvini


    Posted 09-01-2020 09:28 AM
    Having conducted a complete forensic investigation into just over 22'000km of South African roads for the Auditor General , a few important contributing factors became abundantly clear: 
    1. Sub-base and or substrate preparation and compaction are critical at time of construction. The better this is done the longer the pavement will last.
    2. Imperiousness of the wearing surface is critical, this relies on two components; i) water run-off and velocity of run-off, ii) imperiousness of the chosen wearing surface matrix, i.e.        for how long will this layer retain it's water resistance  given that UV radiation in Southern Africa is high. Moisture penetration into the sub-base will accelerate loss of compaction.
    3. Load , distribution of the load and exceeding the load designs will accelerate degradation.
    4. Patching/repairing can possibly work given the above , however keep in mind that the patched/ repaired pavement cannot exist in isolation to the adjoining structures.

    Kevin Gast A.M.ASCE
    Principal Engineer


    Posted 09-01-2020 09:28 AM
    Hello Kevin, 

    Here is a link to some work that I did on the subject a few years ago. 


    Potholes are a problem everywhere.  Not just limited to cold regions.


    David Hein P.Eng, M.ASCE
    Prinicpal Engineer,
    Kitchener ON


    Posted 08-05-2021 05:40 PM

    Hi Kelvin.
    With a focus on only the repair of potholes, it has been quite some
    time since I worked within a public sector highway department.

    To obtain advice from the people who do such work, contact

    The Town of Smithtown Highway Department, New York.


    They were ahead of the process for pothole repair, somewhat like the way a

    Dentist looks at repairing a deep cavity that you wish to stay fixed for more than a season.

    Stay Healthy!




    William M. Hayden Jr., Ph.D., P.E., CMQ/OE, F.ASCE
    Buffalo, N.Y.

    "It is never too late to be what you might have been." -- George Eliot 1819 - 1880


    Posted 01-06-2022 09:32 AM
    Hi Kelvin,

    As others have mentioned, this is not mainly a technological issue. Design standards need to be established and followed by road design engineers. Load considerations need to be addressed via adequate depths for each layer. There may be environmental considerations for not placing adequate cover, for example for utility infrastructure. This would increase the frequency of failures of, say, sewer pipes. To repair such pipes, one would have to dig up part of the road, and patching it up afterwards usually means weakening the structure compared with its previous condition. Inadequate coordination may lead to repeated road excavations to lay down different utilities, causing further weakening of the roads.

    Well-paved roads that are well maintained should on average last a while. We know how to patch roads that do fail. The question is often whether we are willing to spend the money. It is an expensive endeavor.


    Tsee Lee A.M.ASCE
    New York NY