Guest Blog: Sealcoating your Asphalt

Sealcoating is a chemical that is applied to preserve and protect asphalt. Sealcoating can be a tricky business and sometimes it may not be a necessary maintenance feature for your asphalt. Sometimes, it’s a must have and should be performed on an annual basis. Sealcoating maintenance agreements can be made with your asphalt contractor when asphalt is installed.

Applying Sealcoats

Sealcoating can be applied to asphalt in two ways—brushing and spraying. Many times, both methods are used together. Brushing sealcoating is a time consuming process and is best used on cracks, gaps and smaller areas of asphalt. Spraying sealcoating works best for large areas and is performed quickly with a machine. When receiving bids for sealcoating your asphalt, always ask your prospective sealcoating contractor how many coats of sealcoating they plan on using for your project and whether or not it will be brushed on or sprayed. You’ll also need to know how long it’s going to take, especially when it involves a commercial area that is heavily used.

Life Expectancy

The majority of sealcoating materials typically last about 1-2 years. Sealcoating life expectancy often depends on the weather conditions that the asphalt is subjected to. Wet weather, ice, snow and sunlight can all affect the lifespan of sealcoating. Asking your prospective sealcoating contractor exactly how long your sealcoating project is going to be covered under a warranty or guarantee is a great idea; just be sure you get it in writing. In many cases, a maintenance contract can be created when you get an estimate for the asphalt paving cost from your prospective asphalt paving contractor. This way, if any problems occur while the maintenance agreement is in effect, it will be repaired by the asphalt contractor and not at cost to you.

Line Striping

For commercial asphalt, line striping may be necessary. Parking lots and other asphalt areas that need to keep traffic flow properly maintained benefit from a fresh line striping after a new application of sealcoating has been applied. Some sealcoating contractors do not perform line striping, so always ensure that it’s going to be in the bid if it’s needed. Since some sealcoating companies don’t perform line striping projects, a line striping company or another asphalt company may need to make a bid on your project. Always make sure you get a written document that explains each and every material that will be used on your project, as well as a timeline the job will be finished in to ensure costs don’t go up in the middle of the project.

-Post by Kelly

Kelly writes about various asphalt topics including those found at http://www.asphaltshingleroofcost.com/

Pervious Concrete

Below is a simple video from Smart Planet that explains pervious concrete.

CT 207 Changes-September 2011

Caltrans has released a new version of CT 207: Method of Test for Determining Specific Gravity and Absorption of Fine Aggregate.  The new test method can be found on the Caltrans website and here: CT 207.

• The test method has changed drastically so be sure to read through this one and not just my notes.  Here is a list of the major changes:
• The test method’s scope now includes the bulk specific gravity (oven dry) and apparent specific gravity and is no longer specifically for use in portland cement concrete.
• Your balance is now required to have a minimum capacity of 2000g instead of 1000g.
• The test method has been converted from metric to English units.
• The test method no longer specifies that your volumetric flask has to be calibrated to 0.15 mL at 23˚C but instead only specifies that it have a mark to indicate a volume of approximately 500 mL.
• A water tank is now specified in the apparatus section w/ a constant temperature of 73 ± 3˚F and enough depth to maintain the water level above the 500 mL mark on your flask.
• It is now required to wash the sample over a #200 sieve screen and dry back to constant weight before beginning the test method.  Previously there was no wash process involved.
• The sample must be soaked for 24 ± 4 hrs now instead of the previously specified minimum of 15 hours.
• After decanting the water from the sample, the sample is to be spread on a nonabsorbent surface.  In the past it was recommended to spread it on a porous (in other words absorbent) surface. 
• It is now specified to stir frequently to insure homogeneous drying and to break up clumps.  Stirring is now heavily encouraged and explained. 
• How the tamping occurs is now explicitly explained including that each drop should start about 0.2in above the surface of the fine aggregate and that you should clear the material away from the base of the cone before you lift it.
• There is now a table with photos that explains what the material should look like after lifting the cone.  (VERY USEFUL)
• The test procedure now specifies the sample to be 500 ± 10 g instead of 500 g.
• When introducing water to the flask with the SSD sample, it now says to fill the flask to approximately 90% capacity vs. “almost to the 500 mL mark” in the old test method.
• It now notes that manually rolling the flask could take 15-20 minutes, although it is not specified as required.
• It now specifies that when filling the flask to the calibrated capacity, you should measure to the bottom of the meniscus.
• The oven-dry mass is no longer found by weighing a split of the SSD sample.  Now you will use the same material sample that you had in the flask.
• You no longer weigh the flask empty; all of the weights in this test method are in the flask so you will weigh the flask with 500 mL of water in it as well as with water and the SSD sample.  Because of this change, the calculation has changed slightly as well.
• The test method now gives you calculations for not only Bulk Specific Gravity (SSD) and Percent Absorption, but also Bulk Specific Gravity (Oven-Dry) and Apparent Specific Gravity.
• There is now an example test result summary at the end of the test method. 

This new version of the test method is much more descriptive and well formulated.  It should come as no surprise to you but this test method is notorious for creating disputes between contractors and Caltrans.  Hopefully with this new version there will be less problems and all labs will be able to obtain similar results.

My only complaints with this version are as follows.  The majority of the test method species weight in grams but the weight of the tamping rod is specified in ounces. Secondly, in step 4 of the test method, it says to fill the flask to its "calibrated capacity" but it would be much less confusing if it read "to the 500 mL mark".  Finally, the biggest issue that I have is with the photos on the table.  I think this table and the photos will do a great deal of benefit for the testing community but the third photo, the one that the technicians really need to see, is blurry whereas the other two are perfectly clear.  It would have been very helpful to have a clear photo here.

Overall I'm excited about the new test method and hope that it helps in obtaining better correlation with our local districts' Caltrans labs.  Happy Reading!

'Bad' asphalt can escape inspection process

Here's an interesting article that explores the public's perception of poor quality asphalt. It's another source of more information about the quality process when it comes to producing asphalt and laying it down.

'Bad' asphalt can escape inspection process

Cold In Place Recycling (CIR)

A few months back I received this email:

Toni,

I came across this article tonight and I thought of you. http://www.good.is/post/california-cities-start-recycling-roads/ I just wondered what you thought of it. The article says the technique California is starting to use to resurface their roads is way better than the old way. It is also greener. I was wondering if there were any drawbacks that you knew of. 


Keep in touch.

Amanda


Recently I attended a meeting where we discussed this new process so I figured I'd discuss it here for you all.

I haven't actually seen this method in person but I've read a lot about it and saw a couple videos on it. The process is really cool to watch and there are a bunch of videos on youtube. Here is a video of one type of train in action:

The cold in place recycling process or "train" is a pretty simple process. A milling machine at the front of the train mills off the existing pavement down to base rock (typically 2"-4"). This material is then conveyed to a screening/crushing machine where the material is reduced to the size needed for the mix design. From here the material is mixed with a recycling emulsion and laid down on the roadway in windrows. The material is then picked up by a shuttle buggy and put in the hopper of a paving machine where it is laid down as a fresh mat. After that, traditional rollers are used to compact it. The material is a dull brown when it is laid down and as the moisture from the emulsion evaporates it turns to a nice black. Once it has changed to black, traffic can be put back on the road; this can be as soon as 90 minutes after paving.

There are some hesitations about this process here in California but overall it could be a much better method than traditional pavement as far as tax payers are concerned. Like the article Amanda mentioned says, most of the time it is much more monetarily beneficial because you don't have to pay to haul the old asphalt away and haul the new asphalt to the job. In California we're only allowed to put 15% recycled asphalt back into new asphalt mix for State jobs so we haul all of the asphalt back to the plant, crush it down, load some of it into the hot plant, send that mix to the job and lay it down again. With the "train" process it does it all in one place and uses 100% of the old asphalt. Also, this new method emits lower emissions and creates lower pollution. At a conventional hot plant you have to use fuel to dry out the aggregates and heat the asphalt binder. You then mix them together at a temperature of usually around 350 degrees so that the mix can make it to the job still hot. This creates a lot of fumes in the air. The train process doesn't heat up the material while mixing it with additives. This creates far less fumes than producing and transporting conventional mix would.

The biggest worry about the cold in-place method is whether you are getting as quality and consistent of a product. It is difficult to assure that you are not picking up base rock with the asphalt from the old road until it is too late. Many roads are laid in parts at different times as they need to be replaced so you could also be grinding a road that has different types of asphalt and knowing to adjust your equipment accordingly is extremely difficult and almost non-existent. In addition, the train may be milling a road that only has 2" of existing pavement but they are supposed to lay down 4" in its place. This may not be an issue if there have been an adequate number of cores taken. If the operator knows where the pavement is thinner than others he can make adjustments to how he is paving. In an instance where there is not enough pavement to recycle, windrows of RAP brought in from outside sources can be laid down and picked up by the machine to subsidize it. There has also been discussion that too much aggregate material is lost due to weathering over time and to make a similar product to that of the conventional mix you would have to add in the fine material that is lost over time due to water and traffic. Honestly though, I'm a strong believer that if it's been tested and proven in places all over the world then it's probably a good process.

It should also be noted that this process should only be used to recycled distressed PAVEMENT. It will not fix existing problems with the base or subbase and this process has a higher risk of failing if there is a soft subgrade.

I know they're using this method a lot in mountain areas and a lot of states up north because it is sometimes really hard to get material to and from a job site which could be hours from an asphalt plant. In addition, the process is completed so quickly that you only need to close down the lane for a few hours, so mountain roads with only two lanes don't have as much traffic build up. California has already seen a few big experimental jobs with this technology up and down the state and there are many people that say that this is the future of paving in our state so keep your eyes open!