Thursday, October 23, 2014

Spring, Summer, Construction, Winter…..

Fall is here, but are you ready?  Ready for the construction, snow, and really bad pot-holes next Spring?  You drive thru the construction…bounce thru the pot-holes, but have you thought about what those crews on the side of the road are doing?  Ever wonder about the constant work to maintain our roads and what could be the cause of the giant pot-hole you just found?  To answer this, let’s take a look at just three of the factors to asphalt degradation:  How the road was made, who drives on the road, and where the road was built.  

The first area to look at is the design of the road.  The region where you live and the type of soil that is available is a factor affecting the lifecycle of the roads you use.  Sub-base failure or poor quality soil along with poor compaction can greatly reduce the life of the roads.  Too much clay or silt can affect the ability of the road to drain properly.   An Engineer needs to ask themselves: Is there adequate drainage for spring thaws and heavy water flow?  Will it hold the weight of snow plows and buses?  What utilities are buried in the area?  What is the climate where the road will be built?  All of these are important considerations in designing any road, drive or parking lot.   

Alligator Cracking
Have you ever seen a parking lot where the asphalt got too warm and a big truck left a tire mark?  High temperatures soften the asphalt binder and allow the weight of heavy tires to deform the
Even in more moderate temperatures over-loading can cause problems.  If the sub-base is not adequately compacted or if too many heavy vehicles are on a roadway early cracking and deterioration may occur.  Prior to designing a roadway, the Civil Engineer needs to know about the amount of use the road will have, the weight of the vehicles and speed they will travel.   If you begin to think about this as you travel, you will notice that many truck stops, shipping facilities, and highways use concrete instead of asphalt so it can withstand the heavy traffic.  It won’t stop the normal process of deterioration over time, however, knowing the intended use of the roadway or parking lot is essential in designing the right solution.

One of the worst enemies of asphalt is water damage including: 

- Water caught under the asphalt causing soft soil    
   conditions or freezing which becomes frost heave. (Silt or Clay is more susceptible)
-  Poor drainage allows water to get into cracks and begins eroding the sub-base.
-  Freezing / Thawing can push asphalt apart at cracks, leave voids in the sub-base and cause 
-  The ground thaws from the top down which can trap water between the asphalt and frozen ground 
    causing soft soil.

Other weather factors can include hot weather, making asphalt soft and/or causing the asphalt to oxidize making it stiffer and less resilient.  Cold weather can also make the asphalt stiffer and less resilient causing cracks that allow even more water to get in and under it and cause damage.
Other Environmental elements that can affect the life of an asphalt road include tree roots that push up from underneath, changes to the ground under a road such as sinkholes, nearby erosion, or continuous chemical exposure from vehicles in high traffic areas.

Even the best made Asphalt road won’t last forever and for many municipalities the balance between budget and maintenance is an ongoing issue.   With this information in mind you can watch construction crews with a new perspective and think about these key factors to asphalt paving:
-  Build on a firm foundation and use the best sub-grade material available
-  Compact!  The more dense it is, the stronger it is
-  Design for the region ensuring adequate drainage for spring thaw and heavy water flow
-  Know the traffic load and use
-  Maintain the road by sealing cracks, keeping it clear of water, check ditches and drains

Hopefully this has given you a basic understanding of how and why the potholes form and the basic cause and effect of water, weather and usage on Asphalt.   If you still have questions or need to know more for a project, you can contact us by phone at 630.554.6655 or email.  You can also check out our website for a list of our services.